A car bomb attack targeting a police bus has killed seven officers and four civilians in central Istanbul.
It was the fourth major attack in Turkey’s largest city this year.
No group has claimed it, but President Recep Tayyip Erdogan pointed to the involvement of Kurdish militants.
Turkish media said four people had been arrested but gave no details. The banned Kurdistan Workers’ Party (PKK) and one of its offshoots have claimed previous attacks on security forces.