At least 20 police officers have been injured in explosions near a football stadium in Istanbul, Turkey's interior minister says.
Suleyman Soylu said it was thought a car bomb had specifically targeted riot police.
Ambulances and police were seen rushing to the scene, and TV footage showed a fire burning outside the stadium.
Turkey has seen a recent spate of militant attacks in major cities that have left dozens of people dead.
The blast on Saturday 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."