By Saliou Samb

CONAKRY (Reuters) - At least one person was shot and wounded during clashes in the Guinean capital Conakry on Thursday between riot police and youths protesting against the government's preparations for a long-delayed parliamentary election, witnesses said.

President Alpha Conde last week unilaterally called the election for June 30 without agreeing to opposition demands that the government allow the mostly pro-opposition diaspora to vote, and strip South Africa's Waymark of its contract to manage the voter list.

Opposition parties accuse Conde, who took office in 2010 following the first democratic transfer of power since independence in 1958, of planning to rig the vote.

The demonstrators, many of them shirtless, hurled stones at security forces firing tear gas to disperse them along one of the rundown seaside capital's main highways, linking the city center to the airport.

At least three people were wounded, including one who was shot in the chest, witnesses said.

"There are gendarmes and police on every intersection," said Souleyman Bah, a resident of the neighborhood of Bambeto, an opposition stronghold.

Plumes of smoke rose as some of the protesters, who were armed with clubs and sticks, burned tires and debris. Traders in Conakry's Madina market shuttered their shops.

Guinea government spokesman Damantang Albert Camara told Reuters seven opposition leaders were arrested for straying out of the designated protest area.

In February and March, nine people were killed and 300 were wounded during days of similar clashes between opposition protesters, security forces and government supporters.

The election, originally scheduled for 2011, is meant to complete a transition to civilian rule following a military coup in 2008, and could unlock hundreds of millions of dollars in European aid.

Guinea is the world's top bauxite exporter but long-term instability has helped to deter investment in its vast untapped reserves of gold, iron ore and diamonds.

The government was not immediately available to comment on Thursday's violence. It had said it would not tolerate violence during the protests, nor be swayed by opposition threats.

The crisis has alarmed Guinea's neighbors and the international community, which are working behind the scenes to bring both sides to the negotiating table.

The UN Secretary General's special representative to the region Said Djinnit, appointed as facilitator of the dialogue between the opposition and the government, called for calm on Thursday after a two-day meeting with both parties in Conakry.

(Writing by Bate Felix; Editing by Andrew Roche)