The largest crowd was gathering in Diyarbakir, the main city of the region, where the celebrations, marred by bloodshed in the past, drew some 120,000 people, according to police.

Organisers said they expected up to 250,000 people to attend the festivities at the Fair grounds, about 10 kilometers (six miles) from the city center, under close surveillance by some 3,000 policemen.

Newroz day has become a platform for Turkey's Kurdish minority to demand greater freedoms or demonstrate support for the outlawed Kurdistan Workers' Party (PKK), which has beeen fighting for self-rule in the southeast since 1984.

The conflict, which has claimed more than 37,000 lives, has long hampered Turkey's bid to join the European Union and continues to cast a pall on its commitment to democracy and human rights.

"We did our best to ensure that Newroz passes peacefully this year," Ahmet Turk, co-chairman of the pro-Kurdish Democratic Society Party (DTP), the organizer of the festivities, told AFP.

Although celebrations have been relatively calm in recent years, the authorities fear Kurdish militants could try to fuel unrest this year as part of increased PKK violence in the southeast, marked by a series of bomb attacks on civilian targets.

Tension in the region has also escalated over the November bombing of a Kurdish-owned bookstore in the town of Semdinli, which two soldiers and a Kurdish informer are accused of perpetrating.

The incident sparked deadly riots and accusations that Ankara has failed to purge rogue groups in the security forces accused of summary executions, extortion, kidnappings and drug-smuggling in the 1990s, when the PKK campaign in the region was at its peak.

The celebrations kicked off in other parts of Turkey at the weekend, including Semdinli, where the bombed bookstore was re-opened in a DTP-organized ceremony.

In some cities, demonstrators threw stones at the police, but no major incidents were reported.

Keen to boost its image in EU eyes, Turkish police in recent years have often tolerated open displays of support for the PKK -- blacklisted as a terrorist group by Ankara, the EU and the United States -- and its jailed leader, Abdullah Ocalan.

In Tuesday's festivities here, participants brandished giant posters of Ocalan and the PKK, as well as placards that read: "There is still a chance for peace".

Many people queued up to sign a petition declaring the PKK leader to represent the "political will" of their community.

"If millions of people accept Ocalan as a leader, then the state must see him as an interlocutor. There can be no peace as long as he is in jail," one of the organisers of the petition campaign told AFP.

The PKK has called on the Kurds to "shake off their lethargy" on Newroz, which traditionally marks the arrival of spring, and "to step up and radicalize the uprising."

In the bloodiest festival so far, about 50 people were killed by security forces in 1992 during clashes across the southeast.

More recently, two men were crushed to death in a police clampdown on violent Newroz demonstrations in 2002 in the Mediterranean port of Mersin, home to particularly militant community of migrant Kurds.

Newroz marks the awakening of nature at the March 21 equinox. It is also celebrated in Iran and other Muslim communities in the Caucasus and Central Asia.