Two people have been arrested at Heathrow Airport on suspicion of committing terrorism offences, the Metropolitan Police have said.
A man and a woman, both aged 26, were arrested at 20:30 BST on Tuesday after their flight landed at the airport.
The pair were held on suspicion of the commission, preparation or instigation of acts of terrorism.
These arrests are part of an investigation into travel to Syria in support of alleged terrorist activity.
Dozens of people are thought to have travelled from Britain to Syria to fight in the uprising against President Bashar al-Assad.
The BBC's security correspondent, Gordon Corera, said some of those believed to have made such trips have joined jihadist groups.
