Tuesday's blast was the deadliest in a string of bombings across Turkey this year. Police said immediate suspicions fell on the separatist Kurdistan Workers' Party (PKK), which has been fighting the government since 1984, but the rebels denied any role in the blast.

"The preliminary investigation established that the blast occurred while the home-made remote-control device, planted in a flask, was being carried (to another location)," the local governor's office said.

It give no details about the intended target of the attack or who the perpetrators were.

The bomb coincided with the first visit to Ankara by a special US envoy tasked with coordinating joint efforts against the PKK, listed as a "terrorist" group by both countries.

The device exploded at around 9:00 pm (1900 GMT) near a bus stop at a crowded park in Diyarbakir's poor Baglar district, where tea gardens are a favorite venue to relax in the evenings.

It was heard throughout the city, shattering the windows of buildings and opening small cracks in several walls.

Officials said 14 people were injured. Four of them were still in hospital Wednesday.

A major police complex is about one kilometer (less than a mile) from the blast site.

Diyarbakir is a hotbed of activity for the PKK, which has a solid base in the city of around one million people.

In a statement posted on its website, the PKK said it had nothing to do with the bombing and claimed it was the work of rogue Turkish elements aiming to create chaos in the region.

A little-known extreme right group calling itself the Turkish Revenge Brigade claimed in a statement posted on the Internet that it had carried out the attack in retaliation for mounting PKK violence. But police dismissed this as bid for publicity.

The Kurdistan Freedom Falcons, a radical group over which the PKK says it has no control, has claimed 15 bombings across Turkey this year. These include attacks in tourist resorts in the west, which killed nine people and injured around 200.

Diyarbakir's Kurdish mayor, Osman Baydemir, condemned Tuesday's blast as a blow to efforts to restore peace in the southeast, where the 22-year conflict between Ankara and Kurdish separatists has claimed more than 37,000 lives.

"This is a provocation. This is a sabotage of peace," Baydemir said.

The bloodshed came only a day after Turkey's main Kurdish party, the Democratic Society Party, urged the PKK to call a ceasefire.

The PKK has stepped up violence this year after calling off a five-year unilateral truce in June 2004.

At least 75 members of the security forces and 104 rebels have been killed in clashes and attacks since the beginning of the year, according to an AFP tally.

In Ankara, US envoy Joseph W. Ralston, a former NATO commander, said "effective measures" were urgently needed to curb the PKK. He was talking to reporters after his first talks with Turkish officials in his role as special coordinator on joint action against the rebels.

Turkey has long urged its NATO ally to crack down on PKK bases in neighboring northern Iraq, a Kurdish-run region which the rebels use as a springboard for attacks across the border in southeast Turkey.

Ankara says the PKK enjoys free movement in the region and easily obtains weapons and explosives there. It has even threatened a cross-border operation if the United States and Iraq fail to take measures.

Tuesday's attack is likely to put further strain on the government of Prime Minister Recep Tayyip Erdogan, which has come under mounting criticism for failing to stop bloodshed in the southeast at a time when stability is crucial for Turkey's bid to join the European Union.