Mark Doyle: Rebel advance is a surprise in Freetown

The UN representative to Sierra Leone, Francis Okello said that the West African troops defending the government of President Ahmed Tejan Kabbah had withdrawn from the town, which is about 100 km (60 miles) outside Freetown.

Missionaries in Lunsar also said that the West African force, known as Ecomog, had been unable to repel the rebel attack.

The West African intervention force withdrew from Lunsar

Mr Okello said that the latest advance by the rebels meant that the whole of the northern half of the country was now under rebel control in one form or another.

The BBC West Africa Correspondent, Mark Doyle says that this first public UN assessment of the military situation will probably come as a surprise to the people of the capital Freetown, where the government has been seeking to minimise the extent of rebel gains.

Freetown 'safe'

There are also unconfirmed reports of fighting near Port Loko, the next major community toward Freetown, but Mr Okello stressed that Ecomog controlled the situation between the town of Lunsar and the capital Freetown, which, he said, was safe.

President Kabbah - the rebels want him to step down

But a top rebel commander said on Tuesday that his forces would begin attacking Freetown before the weekend if the government fails to agree to immediate talks.

The rebels have demanded that their leader, jailed on treason charges, be released, and they also want President Kabbah resign.

The government, which is supported internationally, says it will not discuss power sharing with the rebels, but has offered them a limited amnesty.

Atrocities condemned

Although the rebels lack popular support, they have mounted a surprisingly successful resurgence after they suffered heavy loses to the Nigerian-led Ecomog force earlier in the year.

Victim of mutilation - rebels have been condemned for their atrocities

Sierra Leonean government officials say they are being aided by neighbouring Liberia, although Liberia has repeatedly denied the charge.

Our correspondent says that the rebels have been almost universally condemned because of the widespread atrocities they have committed against civilians.

The UN Security Council, the United States and Britain have made repeated calls for the rebels to lay down their arms and for the legitimate elected government of President Kabbah to be supported.