Rebel assault on strategic Mali garrison town of Gao

Two army helicopters were scrambled in response, a local official told AFP news agency by phone.

Gao, with a population of 87,000, more than twice the size of Kidal, hosts one of the biggest garrisons in the north.

Separatist rebels seeking to carve out a desert homeland began a rebellion in the west African state in January.

A regional group, the Economic Community of West African States (Ecowas), has placed on alert a peacekeeping force of 2,000 soldiers, Ivory Coast President Alassane Ouattara was quoted as saying by AFP news agency.

After a coup by disgruntled military officers in Mali a week ago, Ecowas has threatened to close land borders, freeze assets and impose a financial blockade if the army does not stand aside before Monday.

The UK's Foreign and Commonwealth Office has now advised against all travel to Mali and urges any British citizens currently there to leave.

'People running'

"We can hear heavy fire coming in the direction of the main military camp," a Reuters reporter said.

"People here are running all over the place and all the shops are closing."

Mahamane Diakite, an aide to the governor of Gao, told AFP: "We can hear heavy weapons fire. We have also seen two helicopters taking off to shoot. Rebels have entered the town."

Malians with family members in Gao say the city is under attack from multiple rocket launchers, the Associated Press reports.

Correspondents say the rebels can expect to meet tougher resistance in Gao, where the majority of troops are from the Bambara tribe, unlike Kidal, where the majority of troops were Tuareg.

Before the coup, Mali's government forces had struggled to drive back the rebels.

The mid-ranking officers who overthrew the government said the army needed more equipment to fight.

Their leader, Capt Amadou Sanogo, has asked for foreign help to tackle the rebels but has been condemned over the coup.

Three members of the military leadership have gone to neighbouring Burkina Faso for talks with President Blaise Compaore, who is mediating in the crisis। bbc