11 die in bomb attack on bus carrying riot police

At least three of the 36 wounded were in a serious condition.

The blast happened on a busy intersection near an Istanbul University building, forcing officials to cancel exams.

The explosion was caused by a bomb placed inside a car and was detonated as the police vehicle was passing by, Sahin said.

The police bus was overturned from the force of the blast, which also damaged nearby buildings, including a hotel whose entrance appeared gutted and whose windows were blown out. Several cars were also wrecked.

There was no immediate claim of responsibility and Sahin would not comment on who may be behind the attack.

The rebels of the Kurdistan Workers' Party, or PKK, have been targeting police and military personnel in Turkey with bombs since July, when a fragile peace process between the rebels and the government collapsed.

The so-called 'Islamic State' group has also been blamed for a series of deadly bombings in the country.

An estimated 500 Turkish security personnel have been killed in attacks or in conflicts with the Kurdish rebels, according to the military, which claims to have killed 4,900 PKK militants in operations in Turkey and northern Iraq, where the group has a major bastion.

Turkish warplanes regularly raid PKK bases in northern Iraq.

Limited access to conflict areas in the south east has made it difficult to verify casualty figures.

The PKK is fighting for autonomy for Turkey's Kurds in the southeast of the country.

The decades-long insurgency against the Turkish state has claimed 40,000 lives.

The group is considered a terrorist organisation by Turkey and its allies.

Last month, eight people were wounded in Istanbul after a car bomb similarly targeted a military vehicle near the entrance of a garrison as the evening rush hour began.