Yusuf Sarwar and Mohammed Ahmed — both 21 and from Birmingham, central England — were arrested at Heathrow Airport on Monday after arriving on a flight from Turkey.

The men are accused of traveling to Syria on or before May 15, 2013, via Istanbul, Turkey, "with the intention of committing acts of terrorism" and preparing to engage in acts of terrorism.

They appeared Saturday at Westminster Magistrates Court in London, and were remanded in custody until Jan. 31, when they will appear at London's Old Bailey Court.

Police have said the case is not connected to the arrest on Friday of another 21-year-old from Birmingham on suspicion of attending a terrorist training camp in Syria.

European officials are concerned about domestic threats posed by fighters returning from Syria. British intelligence officials say they have seen "low hundreds of people" from Britain go to Syria to fight.

(AP)