Istanbul, May 5, (dpa/GNA) - One prison guard was killed and four others were injured in a blast on Wednesday in north-western Turkey that the authorities suspect was a deliberate attack.
It was not immediately clear if it was a terrorist attack.
A bus carrying nearly 30 people, including prison guards, was hit when a bomb went off in the city of Bursa, some 150 kilometres the southwest of Istanbul, Bursa Governor Yakup Canbolat told reporters.
One official was seriously wounded, Canbolat said, adding the authorities assess the bomb was set next to a road in central Bursa.
A remote-control device is believed to have been used to detonate it as the bus was passing, Governor Canbolat said.
Authorities are investigating to find the perpetrators, he added.
Some residential buildings in the neighbourhood were damaged, but there were no civilian casualties, the governor added.
State news agency Anadolu shared images of the bus, the windows of which were broken.
"We will arrest the treacherous murderers behind this cowardly ambush as soon as possible," Justice Minister Bekir Bozdag wrote on Twitter.
Authorities had blamed similar attacks in the past on the outlawed Kurdistan Workers' Party (PKK).
The PKK is designated a terrorist group by Turkey, the European Union and the United States. It has waged a decades-long insurgency against the Turkish state.