The NAB made another request to the Immigration and Passport Directorate after which their passports were blocked and names placed on the blacklist, the report said.
Last week, the Federal Investigation Agency approached Interpol seeking issuance of Red Corner Notices against Hassan and Hussain.
An accountability court has issued warrants in the Avenfield Reference case and issued orders to immediately produce Sharif's sons before the court. The court also issued non-bailable perpetual arrest warrants against them.
Last month, the court sentenced former prime minister Sharif to 10 years in prison, his daughter Maryam to seven and son-in-law captain (retired) Safdar to one-year in prison.
The court also imposed a fine of eight million pounds on Sharif and two million pounds on Maryam.
Sharif was disqualified as prime minister in July 2017 by the Supreme Court following a challenge to his office by cricketer-turned-politician Imran Khan on the basis of publication of the Panama Papers, which alleged that the Sharif family stashed away assets in London through offshore companies Nescoll and Nelson.
The companies are owned by Hussain. Assets in question are four expensive flats in London worth over 200 million pounds.
Hussain admitted ownership of the flats but denied that they were purchased through corruption money.