BUDAPEST/LONDON (Reuters) - Hungarian police have detained two British citizens wanted under a European arrest warrant over charges of leaving Britain without getting the permission required by UK authorities because they had prior convictions for terrorism offences.

The two men, identified by Hungarian police only as Simon Jonathan K., 44, and Trevor B., 40, were arrested last week when they were stopped at the Lokoshaza border station while heading to Romania by train.

A source with knowledge of the case named them however as Trevor Brooks and Simon Keeler, both jailed for more than four years in 2008 for raising funds for terrorism and inciting people to fight British and U.S. forces in Iraq.

The source was unable to say where the men were thought to be going.

Brooks, also known as Abu Izzadeen, is one of Britain’s most high-profile radical Islamist preachers, and rose to prominence in 2006 when he publicly heckled the then home secretary (interior minister), John Reid, in front of television cameras.

The two men were detained for traveling without proper documents, according to a Hungarian police statement late on Tuesday, and were being held pending extradition to Britain.

“We applied for arrest warrants for both of the men under the Counter Terrorism Act which is in relation to breaches of a notification requirement,” a spokeswoman for London police said.

Under British law, those convicted of certain terrorism offences are obliged to inform police of changes to their address or if they want to travel abroad.

Britain’s Home Office said it had no comment on the arrests.