French troops spearhead Timbuktu assault

French-led forces in Mali are advancing on the key northern city of Timbuktu, as they press on with their offensive against Islamist rebels.

On Saturday, Malian and French forces seized Gao, another key northern city.

The advance comes as African Union leaders are meeting to discuss sending more troops to Mali.

Islamists seized the north of the country last year, but have been losing ground since French forces launched an operation earlier this month.

Late on Saturday French Prime Minister Jean-Marc Ayrault said Malian and French troops would arrive "near Timbuktu soon".

Overnight they secured Gao - northern Mali's most populous city- after special forces captured the airport and a strategic bridge to the south.

Most militants appear to have fled into desert hide-outs and the hunt for them may prove more difficult once all major towns are secure, says the BBC's Thomas Fessy in the capital, Bamako.

Troops from Niger and Chad are to assist Malian forces in further securing the town.

African Union leaders are holding a summit in Addis Ababa in Ethiopia, as members move to deploy troops to help the French-led operation there.

African states have pledged nearly 5,700 troops to support French and Malian forces in their campaign.

Only a small part of the African force has so far deployed.

A number of West African countries on Saturday raised the total number of troops pledged to 5,700. Separately, Chad has said it will send 2,000 soldiers.

Meanwhile, the US said it would provide mid-air refuelling for French warplanes.

The Pentagon said it had also discussed plans for the US to transport troops to Mali from countries including Chad and Togo.

Islamists seized a vast area of northern Mali last year and have tried to impose strict Sharia, or Islamic law.

Some 3,700 French troops are engaged in Operation Serval, 2,500 of them on Malian soil.

France intervened militarily as the Islamists advanced further south. It said that the capital, Bamako, was under threat.

As French and Malian troops moved into Gao, Malian officials spoke of scenes of joy, but also some looting.

"Possibly at a certain point the enemy in front of us was underestimated," Malian Foreign Minister Tieman Coulibaly said ahead of the summit in Addis Ababa.

"But everyone has seen that this terrorist group intends to spread its criminal purpose over the whole of Mali, and eventually target other countries."

The AU has recommended civilian observers monitor the human rights situation in the areas which have come back under the control of the Malian government.

Human rights groups have accused the Malian army of committing serious abuses.