CONAKRY, Guinea (BBC) -- Protestors have taken to the streets in at least four towns in Guinea, angered by the Guinean President Lansana Conte's decision to impose martial law.

There was also gunfire in the capital, Conakry, as security forces clashed with demonstrators calling on their ailing leader to step down.

Conte declared a "state of siege" last night and told the army to restore order after three days of violence.

A curfew has also been declared and the military told to prevent a civil war. Four people are reported to have been killed after government forces clashed with demonstrators in the town of Labe,

Correspondents say the streets of Conakry were largely deserted, except for the military patrols, on the first day of martial law.

People are only allowed to leave their homes between 1600 and 2000 local time.

Protect the people

At least 15 people were reportedly killed in Conakry on Monday.

Gunfire was heard near army barracks, while gangs of youths armed with machetes and clubs were seen marching through some suburbs.

The unions called off last month's 18-day strike after Conte promised to hand over powers to a prime minister.

But they renewed the strike action call after saying the man named on Friday for the post, Eugene Camara, was too close to Conte.

Dressed in traditional robes, Conte appeared on national television and radio to announce that the unrest amounted to a "state of siege" and the army had been ordered to "take all necessary measures".

Conte said he had fulfilled the unions' demand that he appoints a prime minister, and accused "badly intentioned people" of hijacking the movement to flout government authority.

Angry population

The BBC's Will Ross in Conakry says that with so many people calling for the president to step down, the new measures are likely to produce even more anger among an already angry population. The unions say President Conte is too sick to run the country

Many in Guinea blame Conte -- who seized power in a 1984 coup but has since won three elections -- for the country's ailing economy, BBC reporter says, and see a change of leadership as the only solution.

The president, meanwhile, has turned to the army to end the crisis, he says.

The French Foreign Ministry has said it is following the situation "extremely closely" and has urged all parties to exercise restraint.

Regional fears

The unions say Conte, who is in his 70s, has diabetes and rarely appears in public, is too sick to continue running the country.

They also accuse him of personally securing the release of two prominent men accused of corruption.

Guinea is rich in minerals but is seen as one of the world's most corrupt countries and most people live in poverty.

About 60 people were killed in protests during last month's strike, when security forces fired live bullets to prevent demonstrators reaching central Conakry.

Some fear that violence in Guinea could spread to its neighbors, Liberia, Ivory Coast and Sierra Leone.