Trump also said in his address that the US response will continue until the Syrian regime stops its use of prohibited chemical agents.
France and UK are also participating in the attack on sites that are believed to harbour chemical weapons in Syria.
Trump’s response came days after speculations that the US may get involved militarily in Syria. Donald Trump on April 11 tweeted while warning Russia that the US will launch a strike in Syria.
Here are the top developments around the US-led airstrikes in Syria in response to the alleged chemical attack:
1) Theresa May says no other alternative:
British PM Theresa May said that there was "no practicable alternative" to the use of force in Syria as she announced Britain had joined France and the United States in launching strikes against Syria.
"This evening, I have authorised British armed forces to conduct coordinated and targeted strikes to degrade the Syrian regime's chemical weapons capability and deter their use," she said in a statement.
UK's Defence Ministry has confirmed that four RAF Tornado jets took part in the Syria strike along with French and US forces.
2) Second US strike in Syria:
Last year on April 4, the Syrian town of Khan Sheikhun was allegedly attacked by chemical weapons. In response to this, the US launched a missile strike on April 7 targeting the Shayrat airbase near Homs from where the attack was reportedly conducted.
The Pentagon had informed that 59 Tomahawk cruise missiles were launched from two US vessels in the eastern Mediterranean. This strike reportedly destroyed 20 per cent of the Syrian Air Force.
This was the first time that the US had directly attacked Syrian forces since the beginning of the civil war in 2011.
3) Huge explosions heard:
Several huge explosions were heard in Syria's capital, Damascus, early today, AFP's correspondent there said, as US President Donald Trump announced strikes on the country.
Syrian state television also reported a US attack, in coordination with France and Britain, on Syria.
The strikes carried out by the US-led forces targeted three Syria's chemical weapons arsenal facilities. A research facility close to Damascus was hit, a chemical weapons storage facility around Homs and a command post were the targets of US-led strike.
US defense officials have said that about 100-120 missiles were launched by American forces against the Syrian regime on targets purportedly housing chemical weapons.
US defense officials say about 100-120 missiles launched by US against #Syria regime chemical weapon targets
— Jeff Seldin (@jseldin) April 14, 2018
4) France joins in:
French President Emmanuel Macron said that France had joined the US and Britain in an ongoing operation of strikes to target "the capacities of the Syrian regime to produce and use chemical weapons".
"We cannot tolerate the normalisation of the use of chemical weapons," he said in a statement issued shortly after huge explosions were heard in Syria's capital early Saturday followed by the sound of aeroplanes overhead.
For Macron, "the facts and the responsibility of the Syrian regime are not in doubt," concerning the "deaths of dozens of men, women and children" in what he said was a chemical weapons attack on April 7 in Douma.
"The red line set by France in May 2017 has been crossed," he said.
AFP reported that 'large part' of Syria's chemical arsenal has been destroyed, quoting French sources. France also said that they have 'solid intelligence' that Syrian regime was behind the chemical attack on April 7. French authorities have also warned of further air strikes in case a new chemical attack surfaces in Syria
5) US says they have proof of chemical weapons in Syria:
The United States has proof that Syrian leader Bashar al-Assad's regime launched a chemical weapons strike last weekend on the then rebel-held suburb of Douma, State Department spokeswoman Heather Nauert said today.
"I'm not going to say which day we absolutely knew that there was proof. The attack took place on Saturday, we know for a fact that it was a chemical weapon," she told reporters.
"We know that there are only certain countries like Syria that have delivery mechanisms and have those types of weapons." Asked whether she could say that the United States has proof that Assad's regime was behind the strike, Nauert said: "Yes.
6) US makes a case for military action in the United Nation:
Prior to the strikes,
US Ambassador Nikki Haley told the UN on Friday that no decision had been taken about military action against Syria, but the use of force would be in response to multiple chemical attacks carried out by President Bashar al-Assad's forces.
Haley made clear that the US administration was taking time to assess the full implications of military strikes on Syria after Russia warned that it could lead to a dangerous US-Russian war.
Addressing the Security Council, Haley laid out Washington's case for resorting to force, challenging Russia's claim that military action would be in violation of international
7) Syria claims right to self-defence:
At the United Nations, Syria warned on Friday that it will have "no other choice" but to defend itself if the West initiates military action.
"This is not a threat. This is a promise," Syrian Ambassador Bashar Jaafari told the UN Security Council.
The ambassador invoked Article 51 of the UN charter that recognises the right to self-defence by any state if it comes under attack.
If Britain, France and the United States take military action, "we would have no other choice expect applying Article 51 that gives us the right to defend ourselves," said Jaafari.
"The United States and its allies have no proof and, without even waiting for the Organisation for the Prohibition of Chemical Weapons to take a position, have carried out this military attack," said the foreign ministry in a statement.
They "are responsible for the regional consequences of this adventurist action," the statement read, condemning a "clear violation of international
rules and laws".
Iran's supreme leader Ayatollah Ali Khamenei denounced US President Donald Trump, France's Emmanuel Macron and Britain's Theresa May after they launched strikes today against the Syrian regime, branding them "criminals".
"The attack this morning against Syria is a crime," Khamenei said in remarks published on his Telegram channel. "The American president, the French president and the British prime minister are criminals.
10) Russia reacts to Syrian strikes:
9) UN Chief says Syria most serious threat:
UN chief Antonio Guterres today mentioned that Syria represents "most serious threat" to international
peace and security and urged all stakeholders to avoid any move that could result in worsening the situation for the Syrian people.
United Nations Secretary-General Antonio Guterres yesterday said that the "Cold War is back with a vengeance", as he warned against the escalation of tensions among rival factions -- the US and Russia -- over the suspected use of chemical weapons in Syria.
The UN Chief further said, "The mechanisms and the safeguards to manage the risks of escalation that existed in the past no longer seem to be present."
Reacting to the US-led strikes,
Russia’s foreign ministry said that the Syrian capital was attacked at the very moment when the country had a chance for a peaceful future.
A Russian international television network reported that President Vladimir Putin said that, "US-led strikes in Syria without United Nations Security Council mandate (is) a violation of international law"
Russia’s foreign ministry also said that the Western media has some responsibility for the Syria attack, which was based on its reports.
"Not one of the cruise missiles released by the US and its allies entered the zone of responsibility of Russian air defences protecting facilities in Tartus and Hmeimim," the ministry said in a statement carried by state news agency.
Russia on Friday had claimed that they had evidence that UK had staged the chemical attack while colluding with White Helmets.
"Having visited the site of the would-be chemical attack, Russian military experts did not find any traces of chlorine or any other toxic agent. Not a single local resident was able to confirm that a chemical attack had actually taken place. The Organisation for the Prohibition of Chemical Weapons dispatched its experts to Syria in order to investigate all the circumstances. However, in a sign of cynical disdain, a group of Western countries decided to take military action without waiting for the results of the investigation," the statement further read.
Putin also said that the US-led strike on Syria was an "act of aggression" against a sovereign state and Russia strongly condemns it.
Russia is also calling an emergency session of UN Security Council over strike on Syria.
Russian military said Syrian air defense units downed 71 out of 103 cruise missiles launched by US and its allies.
AFP quoting Russian Defence Ministry reported that "a significant number" of missiles fired by the coalition were intercepted.
#BREAKING Over 100 missiles fired at Syria, 'significant number' intercepted: Russian defence ministry
— AFP news agency (@AFP) April 14, 2018
The Russian Ambassador to the US said, "A pre-designed scenario is being implemented. Again, we are being threatened. We warned that such actions will not be left without consequences."
Statement by the Ambassador Antonov on the strikes on #Syria:
A pre-designed scenario is being implemented. Again, we are being threatened. We warned that such actions will not be left without consequences.
All responsibility for them rests with Washington, London and Paris. pic.twitter.com/QEmWEffUzx
— Russia in USA