The arrests came as Kurds tried to celebrate the new year festival of Newroz.

According to one of Turkey's leading human rights groups, more than 4,000 people were detained in a major security operation in the city of Diyarbakir alone.

Diyarbakir, the administrative capital of southeast Turkey, has been closed to journalists since the capture of PKK guerrilla leader Abdullah Ocalan triggered a wave of violence.

Eyewitnesses there said army and police units were stationed on almost every street corner, and armoured cars patrolled the city.

Turkish special forces arrested Kurds celebrating Newroz

There were nearly 1,000 arrests in Istanbul, where police and demonstrators exchanged gunfire at several locations.

A number of people were wounded, some of them seriously, as Istanbul's security forces moved in quickly to prevent protests spreading.

In what appears to have been a suicide bomb attack, a suspected Kurdish guerrilla killed himself and wounded three others in the eastern province of Van.

Turkey's state-run Anatolian news agency said the attacker pulled the pin out of the bomb when challenged by police in the town of Baskale.

There were sporadic clashes in other cities.

Celebrations banned

Police were trying to stop supporters of the Kurdish rebel movement, the PKK, celebrating the new year festival of Newroz.

Newroz, meaning "new day" in Kurdish, has become a traditional time of protest for disaffected Kurds.

Boys and young men traditionally celebrate the event by leaping over large bonfires.

There was concern that this year's festivities could be a flashpoint after the arrest of Abdullah Ocalan.

Unofficial Newroz celebrations were banned and the southeast of Turkey, a largely Kurdish region, was virtually shut off from the outside world.

Massive security precautions were taken across the country.

But in the southeastern district of Mardin, a bomb explosion damaged the main oil pipeline from Iraq, temporarily halting the flow of crude oil, and causing what local officials called limited damage.

The local authorities have accused the PKK of being behind the attack.