The Higher Electoral Board (YSK) was expected to reverse its decision for at least some of the seven candidates after unnamed officials of the body, quoted widely in the media, signalled that the presentation of additional documents would help overcome the problem.

Lawyers for four of them submitted the requested papers to the YSK, with others expected to follow later in the day, the NTV news channel reported.

Among the first four was iconic Kurdish activist Leyla Zana, winner of the European Parliament's human rights award who spent 10 years in jail before being released in 2004.

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

In a move threatening to fan Turkey's long-standing ethnic conflict, the YSK Monday disqualified 12 candidates from the June 12 parliamentary elections, among them seven people backed by the Peace and Democracy Party (BDP), Turkey's main Kurdish political movement.

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

The barred candidates include other prominent Kurdish figures, among them two members of the outgoing parliament.

President Abdullah Gul stepped in to ease the tensions, inviting BDP leader Selahattin Demirtas for talks at his residence late Wednesday.

"The president appeals to everybody to be constructive and make all legal and political efforts to overcome the problem," his spokesman said.

The BDP has urged an extraordinary parliamentary session to tackle the controversy and threatened to boycott the polls.

Thousands of Kurds took to the streets across Turkey Tuesday to protest the decision, clashing with riot police and throwing petrol bombs at public buildings and banks.

On Wednesday again there were brief clashes in Diyarbakir, the largest city of the Kurdish-majority southeast, that landed at least 16 protestors in police custody and left four others slightly injured, an AFP reporter said.

The unrest broke after militant Kurdish youths, part of a march that attracted about 3,000 people, hurled petrol bombs 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 campaign for Kurdish self-rule in the southeast.

The barring of their candidates deepened a sense of injustice among Kurds, whose political parties already face a series of legal hurdles.

The BDP fielded its candidates as independents in order to circumvent an electoral threshold under which parties have to get at least 10 percent of votes to enter parliament.

The ruling Islamist-rooted Justice and Development Party, aiming for a third straight term in power, has rejected widespread appeals to reduce the threshold.