Britain could temporarily ban British Islamists who go to fight for militants in Iraq and Syria from returning home, the BBC reported, citing a government source.

British nationals suspected of being involved in terrorism would be allowed to keep their citizenship but would be prevented from re-entering the country for a period of time, the report said.

The government source said the proposal was one of several under consideration and that "details of the package are being finalized" and would be announced by Prime Minister David Cameron on Monday.

"Previously, our range of powers to prevent return to the UK applied only to foreign nationals, dual nationals or naturalized citizens," the source said.

The government is also looking at ways to make it harder for potential fighters to travel abroad by making it easier for authorities to remove their passports through additional temporary seizure powers at the border.

Cameron said last week he would unveil new laws on Monday to make it harder for Britons to travel to Syria and Iraq to fight, and to tackle radicalization among Britain's 2.7 million Muslims.

Britain raised its terrorism alert on Friday to the second-highest level, with Cameron saying the Islamic State group in Syria and Iraq posed the country's greatest ever security risk.