The unrest broke in Diyarbakir, the largest city of the Kurdish-majority region, while a crowd of some 5,000 people marched at the funeral of four Kurdish rebels killed in clashes with the army.

One plainclothes policeman was stabbed and three others were beaten as demonstrators attacked their van, smashing its windows, after the vehicle got stuck amidst the simmering crowd.

Police fired shots in the air and used water cannons to rescue their colleagues.

"Revenge, revenge!" the mourners chanted as they marched to a cemetery outside Diyarbakir, with the four coffins carried on shoulders and wrapped in flags of the separatist Kurdistan Workers' Party (PKK).

The dead were among seven PKK rebels whom the army killed in two-day clashes in mountains in the province of Tunceli last week.

Funerals of PKK militants in Turkey routinely turn into demonstrations of Kurdish militancy and are often marred by violence.

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