The 37-year-old non-commissioned officer, critically injured in Tuesday's blast, had been in intensive care in an Istanbul hospital.

Separatist Kurdish rebels claimed responsibility for the remote-controlled roadside bomb which targeted a bus carrying army personnel to work.

The blast killed four other soldiers and the 17-year-old daughter of an officer and wounded 13 people.

It followed threats by the separatist Kurdistan Workers' Party (PKK) to spread violence to urban areas after a wave of deadly attacks on the security forces in remote regions in the Kurdish-majority southeast.

Ten people have been charged in connection with the bombing so far, among them four who have been detained pending trial.

Police are continuing to look for the person who detonated the bomb.

The PKK, listed as a terrorist group by Turkey and much of the international, took up arms for Kurdish self-rule in the southeast in 1984, sparking a conflict that has claimed some 45,000 lives.