Explosions near a stadium after a football game in Istanbul, Turkey, killed at least 13 people and injured others, reports say.
Interior Minister Suleyman Soylu said it was thought a car bomb had specifically targeted riot police.
Witnesses heard gunfire after the attack, and ambulances and police vehicles rushed to the scene.
Turkey has seen a recent spate of militant attacks in major cities that have left dozens of people dead.
No group has said it was behind the attack but a wave of bombings in Turkey this year has been carried out by Kurdish militants and so-called Islamic State, the BBC’s Turkey correspondent, Mark Lowen, reports.
The fact that police appear to have been hit will focus suspicion on Kurdish guerrilla groups, who have mainly targeted the security forces, he adds.
Transport Minister Ahmet Arslan wrote on Twitter that it was a terror attack.
Turkey country profile
It happened two hours after a football match at the Vodafone Arena between Besiktas and Bursaspor, two of Turkey’s top teams, ended.
Local media reported that fans had already dispersed. Bursaspor posted on Twitter that none of its fan groups knew of any injured fans.
Mr Soylu said: “It is thought to be a car bomb at a point where our special forces police were located, right after the match at the exit where Bursaspor fans exited, after the fans had left.
“We have no information on the number of dead. God willing we hope there won’t be any.”
Photographs posted on Instagram after the explosion showed helmets strewn on a road and damaged vehicles.
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