The assets of three British citizens reported to have been involved in terrorism-related activities in Syria were frozen by the British government on Friday, Al Arabiya reported.
Nasser Muthana and Reyaad Khan, both from Cardiff, and Ruhul Amin, from Aberdeen, were added to the Tresury's list of people targeted for financial sanctions, according to the list posted on its website.
Muthana, a 20-year old student, appeared in an online video last month urging Muslims to join the militant group the Islamic State in Iraq and Syria (ISIS), his father Ahmed Muthana told the BBC.
In the video, Muthana was identified as Abu Muthana al-Yemeni says the men are getting ready to fight in Iraq.
"We have participated in battles in Sham [Greater Syria] and we will go to Iraq in a few days and fight there and come back and we will even go to Jordan and Lebanon with no problems," he said.
Khan is a schoolfriend of Muthana and also appeared in the video for ISIS along with Amin, various media reports said. Amin also has Bangladeshi nationality, according to the website.
Britain's Treasury froze their assets under counter-terrorism laws.
ISIS has in recent weeks seized control of large parts of northern Iraq and declared an Islamic 'caliphate' spanning adjacent parts of Syria and Iraq, renaming itself simply the Islamic State.
Some 400 UK nationals are thought to be fighting in Syria.
The move came as one Briton, who claimed he has been fighting alongside jihadi militants in Syria, said he will not return to the UK until he can raise "the black flag of Islam" over Big Ben and Downing Street.
The comments were broadcast by the BBC as religious leaders called on British Muslims not to travel to Syria and Iraq, amid fears of jihadists fleeing the country to take part in terrorism.