Churkin accused five Turkish companies of delivering aluminium powder, ammonium nitrate, hydrogen peroxide and other material produced by various Turkish and foreign companies to the Islamic State (ISIS) group.
Turkey's Foreign Ministry spokesman in Ankara called the letter "the most recent example of Russia's propaganda campaign against Turkey, and as such it cannot be taken seriously".
Russia, a key ally of Syrian President Bashar Assad, and Turkey, a major backer of Syria's opposition, have been at odds during the five-year conflict. Tensions escalated following Turkey's downing of a Russian warplane near its border with Syria last November.
Russia retaliated by deploying long-range air defence missile systems to its base in Syria and imposed economic sanctions on Turkey. President Vladimir Putin has accused Turkey of "allowing terrorists to earn money by selling oil stolen from Syria", and Russia's top military brass accused Turkish President Recep Tayyip Erdogan and his family of personally profiting from oil trade with ISIS militants.
Churkin said that one notable feature of the explosive devices assembled by militants from ISIS is the use of parts manufactured by US, Swiss and Swedish companies.
He said "detonation cords manufactured in third countries have been illegally resold through Turkey to ISIL (ISIS) fighters".
"These facts demonstrate that the Turkish authorities are deliberately involved in ISIL activity, as they are providing access to components for improvised explosive devices that are being widely used to commit terrorist acts," Churkin said.
Business Standard has always strived hard to provide up-to-date information and commentary on developments that are of interest to you and have wider political and economic implications for the country and the world. Your encouragement and constant feedback on how to improve our offering have only made our resolve and commitment to these ideals stronger. Even during these difficult times arising out of Covid-19, we continue to remain committed to keeping you informed and updated with credible news, authoritative views and incisive commentary on topical issues of relevance.
We, however, have a request.
As we battle the economic impact of the pandemic, we need your support even more, so that we can continue to offer you more quality content. Our subscription model has seen an encouraging response from many of you, who have subscribed to our online content. More subscription to our online content can only help us achieve the goals of offering you even better and more relevant content. We believe in free, fair and credible journalism. Your support through more subscriptions can help us practise the journalism to which we are committed.
Support quality journalism and subscribe to Business Standard.