The young man was killed in Bismil, near the regional capital of Diyarbakir, when the police responded to an "intensive" hail of petrol bombs, firecrackers and stones from a crowd of some 800 people, the local governor said.

The statement did not specify how the man died but a senior Kurdish politician said he was killed by a "police bullet" and witnesses confirmed that the security forces fired first plastic bullets and then live rounds against the demonstrators.

Three other people were injured, among them two in serious condition.

Enraged protestors then stormed into the local office of the ruling Justice and Development Party (AKP) and set a fire inside, Anatolia news agency said, adding that the blaze caused extensive damage but no casualties.

In Diyarbakir, a bus driver was in critical condition after his vehicle caught fire from a petrol bomb, hospital sources said.

The unrest broke out after militant Kurdish youths, part of a march that attracted about 3,000 people, hurled Molotov cocktails and firecrackers at the police, prompting a response with tear gas and water cannons.

"Revenge, revenge!" the youths shouted, and chanted slogans praising the outlawed Kurdistan Workers' Party (PKK), which has waged a bloody 26-year separatist campaign in the Kurdish-majority southeast.

At least 16 protestors were detained and four slightly injured, an AFP reporter said.

Tensions had appeared to ease earlier in the day after the Higher Electoral Board (YSK) hinted it might reverse its decision to disqualify seven election candidates backed by Turkey's main Kurdish political movement, the Peace and Democracy Party (BDP).

The death of the protestor prompted BDP leader Selahattin Demirtas to cancel a meeting with President Abdullah Gul in Ankara, which had been organised in a bid to seek a solution through dialogue.

"I have informed (the president) that I cannot go to Ankara in the current circumstances," Demirtas told Anatolia.

The barring of their candidates deepened frustration among Kurds at a time when their parties already face a series of legal hurdles in the June 12 parliamentary elections and many Kurdish activists remain in jail.

The YSK was expected to reverse its decision for at least some of the candidates after it asked them to present additional documents.

YSK deputy chairman Kirdar Ozsoylu voiced hope the board would decide "in favour of democratic rights and fundamental freedoms" when it begins to review the appeals Thursday, Anatolia reported.

Among the barred applicants is iconic Kurdish activist Leyla Zana, winner of the European Parliament's human rights award who has spent 10 years behind bars, and two members of the outgoing parliament.

Zana Wednesday obtained a court document certifying that there were no legal restrictions on her political rights, Anatolia said.

The BDP has urged an extraordinary parliamentary session to tackle the controversy and threatened to boycott the polls, raising the prospect of intensified unrest in the country's long-standing ethnic conflict.

The YSK announced the disqualifications late Monday, triggering violent Kurdish protests across the country the following day.

The board based its decision on past convictions of the bidders and legal technicalities, but came under fire for disregarding recent amendments that favour the applicants.

The BDP fielded its candidates as independents in order to circumvent an electoral threshold that requires parties to get at least 10 percent of the vote to enter parliament.

The Islamist-rooted AKP, aiming for a third straight term in power, has rejected widespread appeals to lower the threshold.