LONDON: British counter-terror police arrested two men on Monday at London's Heathrow Airport on suspicion of terrorism offences linked to Syria, police said.

The men, both aged 21 and from Birmingham, central England, were held after arriving back in Britain on a flight from Istanbul in Turkey, West Midlands Police said.

According to sources one of the men is of Pakistani origin and the other is of Bangladeshi descent.

They are believed to have travelled to Syria in May 2013, police said.

British police have over the past three years arrested a number of people who have travelled to Syria over concerns that they are fighting with jihadi groups.

Unarmed officers from the force's counter-terrorism unit detained the two men on Monday as they disembarked from their plane and they are now being questioned at a police station in the West Midlands area, which includes Birmingham.

Police played down any immediate terror threat.

"We took action this afternoon in order to ensure we can properly understand what activities these men have been engaged in whilst in Syria -- not because they posed any imminent threat to the public," said Detective Chief Superintendent Kenny Bell, head of the West Midlands counter-terrorism unit.

Foreign Secretary William Hague said on Monday that "hundreds" of Britons were believed to have gone to fight in Syria but said security forces were doing their best to monitor the situation.

In November British prosecutors dropped a case against a doctor accused of kidnapping a British photographer and his Dutch colleague in Syria. (AFP)

SOURCE: AFP