Officials are working to verify whether any Britons were killed in a suspected suicide bombing in an area of Istanbul popular with tourists, Foreign Secretary Philip Hammond has said.
The blast in Sultanahmet, in which at least 10 people died and 15 others were injured, was described by Turkish President Recep Tayyip Erdogan as "Syria-linked", while a local government official described it as "terror-linked".
Mr Hammond said the Government knows tourists were "involved" in the explosion and promised to update MPs during Foreign Office questions if any news about UK nationals emerges.
Opening the Commons session, he said: "I wonder if I might just take a few seconds to update the House on the breaking news coming in from Istanbul where an explosion has occurred in the Sultanahmet area, killing at least 10 people, with many more injured.
"This is a tourist area of the city and we already know that some tourists are involved in this incident.
"We are at the moment seeking to verify whether any British nationals are involved and if we get any news on that during the course of the next hour I will update the House accordingly.
"In the meantime I offer my sympathies to the victims and their families and everyone else affected by the attack."
Shadow Foreign Office minister Pat Glass said: "Our thoughts are with anyone caught up in this awful situation."
The explosion in Istanbul's Old City hit a park which is home to a landmark obelisk just 30 yards from the Blue Mosque in the city's main sightseeing area, which also includes Topkapi Palace and the Hagia Sophia museum.
Turkey's Dogan news agency reported that at least six Germans, one Norwegian and a Peruvian were among the wounded, while Seoul's Foreign Ministry said one South Korean had a finger injury.
Alex Salmond, the SNP's international affairs spokesman, told MPs: "The thoughts of everyone on these benches are with those caught up in the incident in Istanbul."