West African leaders slapped crippling sanctions on Mali's junta Monday on the eve of UN talks about the country, where half the territory has fallen to rebels and Islamist fighters.

As Mali slid further into chaos under military rulers who seized power on March 22, France called for an emergency meeting of the United Nations Security Council yesterday.

The 15-nation Economic Community of West African States (ECOWAS) tightened the stranglehold on the junta in a bid to force it to give up power.

"All diplomatic, economic, financial measures and others are applicable from today (Monday) and will not be lifted until the re-establishment of constitutional order," said the chairman of the 15-nation regional bloc, Ivory Coast President Alassane Ouattara.

The bloc will also put in place a military standby force, after earlier putting some 2,000 regional troops on alert, Ouattara said, calling the situation in Mali" extremely serious."

Mali's junta said late Monday that it had "taken note" of the regional embargo.

On Monday, witnesses reported that Islamist fighters chased the Tuareg rebels out of Timbuktu, one day after swept into the fabled city. As Kidal, Gao and then the ancient city ofTimbuktu fell in the past three days, the bow-tie shaped nation was split in two.

As the situation deteriorated, both former colonial power France and Belgium urged their citizens to leave the country.

The swift rebel advance in the north sparked panic further south as some citizens saw soldiers fleeing their posts and followed suit.

More than 200,000 people have been forced from their homes by the fighting and aid groups have warned that the combination of civil war and drought could lead to one of the continent's worst humanitarian emergencies.