At least seven Turkish soldiers have been killed after the bus in which they were travelling was ambushed by gunmen. Several other soldiers were wounded.
A local TV station said they were on patrol in the mountains in foggy weather when they came under fire.
The attack happened in Tokat province in northern Turkey. Who carried it out is not immediately clear.
The Kurdish separatist group the PKK usually attacks targets in the south east, but it is believed to have signed co-operation pacts with left-wing rebels in the north.
There have been rising tensions ahead of a court case due to decide on whether Turkey’s largest pro-Kurdish political party should be closed down.