He said Ecomog was attacking rebel positions in Lunsar, 120km east of Freetown.

Reliable sources said Nigerian Alpha jets had strafed rebel positions around Lunsar.

The UN earlier said its military observer mission would resume in Freetown, following an Ecomog-led improvement in the situation.

Mr Okello said several expatriate observers and other staff had returned to the city.

Earlier, reliable reports said Ecomog and government troops had stopped a rebel advance on the strategically important town of Port Loko, 120km (80 miles) north-west of Freetown.

The port is the last major town between the rebels and Freetown international airport.

The rebels, backed by parts of the former Sierra Leone army loyal to the former military regime, have been waging a major offensive and have tried to enter the capital.

So far they have been thwarted by the 15,000-strong Ecomog force which supports the internationally recognised government of President Ahmed Tejan Kabbah.

The UN views the situation in Sierra Leone seriously because of the potential of the conflict to destabilise the region.

Aside from Nigeria's involvement, Liberia has been accused of backing the insurgents.

The war has also uprooted tens of thousands of refugees.

BBC West Africa Correspondent Mark Doyle says there are fears the fighting will divide the country between north and south if a long-term political solution is not found.

Much of the north has been taken by the rebels, while the south is under government control.