The historic town of Timbuktu is one of the most famous in Mali
Tuareg separatist rebels in Mali say they have surrounded the historic town of Timbuktu after a rapid advance through the north of the country.
Although Arab news network, Al-Jazeera is reporting that the rebels have entered the ancient city and have possibly even captured it.
Eyewitnesses in the town say they have heard heavy weapons and machine-gun fire, apparently being directed at a military base.
Troops appear to have deserted the base, a resident told BBC News.
Two other important centres, Kidal and Gao, fell to the rebels and their Islamist allies in recent days.
A resident who spoke to the BBC's Thomas Fessy said the Malian army had fled but a Malian Arab self-defence militia, backed by local businesses, was still defending Timbuktu.
There was no actual fighting inside the town, the resident added.
Timbuktu, about 1,000km (600 miles) from the capital Bamako, is the only major northern town still under the control of the Malian army.
Figures on casualties in the fighting are not been available.
In their statement, the National Movement for the Liberation of Azawad (MNLA) said they had "liberated" the town of Gao on Saturday.
Few details of the situation in the town of 90,000 people have emerged since the rebels moved in, but witnesses quoted by AFP news agency said unknown attackers had forced open the gates of the prison and several public building had been looted by civilians.
Officials with several international non-governmental organisations based in Gao have fled the town, a security source told the agency.
The country has been in turmoil for more than a week since army officers overthrew the government, blaming it for failing to contain the rebels, who launched their offensive in January.
Coup leader, Captain Amadou Sanogo said in a statement read out on state television that soldiers had decided not to fight the rebels in Gao because the town's military camps were close to residential areas.
Regional group ECOWAS has demanded the reinstatement of Mali's elected government, and has put 2,000 troops on standby for a possible intervention.
Appealing for support from the international community, the current chairman of ECOWAS, Cote d’Ivoire President Alassane Ouattara, said on Saturday that Mali's territorial integrity must be preserved "at all costs".
"We must succeed because if Mali is divided, carved up, it is a bad example," he added.
ECOWAS has threatened to close land borders, freeze assets and impose a financial blockade if the army does not stand down before Monday.
Mali's overthrown President, Amadou Toumani Toure, is said to be safe at an undisclosed location inside Mali.
Tuaregs have launched several rebellions over the years, complaining that the government in Bamako ignores them.
However, the new conflict has been fuelled by the return of Tuareg fighters from Libya last year after fighting for the late Muammar Gaddafi or his opponents.
It appears these fighters are heavily armed with looted weapons.
The MNLA are backed, for now, by a smaller, Islamist group called the Ansar Edine, which wants to impose Sharia law.
Analysts say the militants have taken advantage of Mali's coup to make a swift advance.