At least nine people have been killed in the Liberian capital, Monrovia, after United Nations peacekeepers reportedly confronted militiamen.

These are the worst clashes since UN peacekeepers deployed in Monrovia in August after 14 years of civil war.

If confirmed, it would be the first time members of the 4,500-strong UN force have been involved in fighting.

The fighters have been rioting since Sunday, demanding immediate payment for giving up their guns under a UN plan.

The BBC's Jonathan Paye-Layleh says the bodies of those killed appeared to be those of militiamen who had fought for former President Charles Taylor.

Extra peacekeepers are on the streets and schools are closed.

War crimes court

Local residents and police officials said that Nigerian peacekeepers had sent armoured vehicles to quell protests by militiamen unhappy at an overnight curfew imposed by the government.

"They were looting when the peacekeepers confronted them," said resident Marie Sonpon.

"When (the peacekeepers) tried to stop them, they opened fire."

UN spokeswoman Margaret Novicki said she knew of no engagements involving UN troops.

But a UN commander, who refused to give his name, said that a peacekeeper from Benin had been shot in the leg after confronting militiamen at a checkpoint.

Interim leader Gyude Bryant warned on state radio that the rampaging militiamen would be arrested and brought before a war crimes court.

The head of the UN mission in Liberia, Jacques Klein, said it was "unfortunate that a small criminal element has attempted to disrupt what is a major international effort to bring peace, security and stability to the Liberian people."

Looting spree

The latest unrest began at the start of a UN disarmament programme designed to rehabilitate an estimated 40,000 fighters.

Fighters will receive $300 each for laying down their arms.

Under the UN plan, fighters should surrender their weapons and start to receive food rations, counselling and education.

The first $150 will be paid at the end of a three-week demobilisation programme, with the second $150 handed over when fighters return to their communities.

Militiamen went on a looting spree, smashing car windows, stealing food from houses and abducting women.

One woman was reported to have been killed when she refused to hand over her car.

After meeting government officials on Tuesday, the UN now says that disarming fighters will receive the first $75 of the package immediately on handing in their weapons.

'Homework'

The UN force is planned to number 15,000, but with only 4,500 on the ground at present it cannot easily disarm the militiamen, many of whom are battle-hardened and often high on drugs.

"Unmil needs to do its homework," said interim Justice Minister Kabineh Janeh.

His rebels from Liberians United for Reconciliation and Democracy (Lurd) started fighting in 1999 to oust Mr Taylor and have refuse to disarm until a dispute over ministerial posts is resolved.

"You cannot start by disarming thousands of combatants if you don't even have, in the first place, a cantonment site for them."

Mr Taylor stepped down in August, going into exile in Nigeria, but the security situation is still extremely fragile.