A car bomb has killed five people and injured 68 in the Kurdish-dominated city of Diyarbakir in south-eastern Turkey, officials say.
There have been a number of explosions in Diyarbakir in the past
It was set off remotely and targeted a military bus as it passed through the city centre, a local governor said.
Two of the five people killed were students, while some 30 soldiers were among the injured.
Police said they suspected Kurdish militants. Diyarbakir is the biggest city in the mainly Kurdish south-east.
Speaking in the capital, Ankara, Prime Minister Recep Tayyip Erdogan condemned the blast as a "terrorist act".
Turkish troops who are fighting PKK Kurdish rebels both inside Turkey and in nearby northern Iraq are based in the area.
Last week, Turkish warplanes launched strikes on Kurdish rebel targets in northern Iraq.
There have been a number of explosions in Diyarbakir in the past, the most recent of which was caused by a bomb at a bus stop in 2006.
An unexploded bomb was found two years ago near the location of Thursday's blast.
The explosion happened during rush hour in an area close to a military residential complex and a helicopter base, reports say.
A correspondent for the BBC Turkish Service who was only about 70 metres away from the blast said there was an enormous explosion, which caused a number of vehicles to catch fire and windows to shatter.
"Our car shook violently, then we saw flames going up towards the sky. We ran towards the flames and saw injured people scattered all over. Their screams were unbearable.
"Fire crews arrived within four to five minutes, but the flames were such that they could not get to the injured either. They had to deal with the flames before tending to them."
Turkish television has been carrying pictures of the huge blaze caused by the blast, which it says could be heard 3km (two miles) away.