Assailants detonated a remote-controlled explosive device near a bus carrying prison guards in Turkey, an official has said.
One guard was killed and four others were wounded in the blast on Wednesday.
No one has claimed responsibility for the attack, which occurred in the Osmangazi district, in Turkey’s northwestern Bursa province.
“Our evaluation is that a hand-made bomb that was left beneath an electricity pole was detonated by remote control as the prison vehicle was passing by,” Bursa Governor Yakup Canbolat told reporters, after inspecting the scene.
Around 30 people were on the bus when it was hit by the remote-controlled explosive device, Canbolat added.
All of them were taken to hospitals as a precautionary measure, with one of the injured in a serious condition, he added.
"Operations to arrest those responsible are underway," Turkish Interior Minister Suleyman Soylu said on Twitter.
Kurdish militants, leftist extremist groups and so-called Islamic State (IS) militants have carried out numerous attacks around the country in the past.
The attack comes after Turkey launched an air and ground offensive against the Kurdistan Workers' Party (PKK).