West African states have put 2,000 troops on standby and called for international aid as rebels advance in northern Mali, Ivory Coast President Alassane Ouattara said Saturday.

"We have put on alert the standby forces of the Economic Community of West African States," Ouattara, the current chairman of the 15-member ECOWAS, said on television in Abidjan.

"We have 2,000 men in these forces. We have equipment. We have asked the international community to support us, to support Mali," he said.

Ouattara was speaking after Tuareg separatist and Islamist rebels captured the town of Kidal in northern Mali on Friday, and as reports came in of an attack on the region's main city of Gao early Saturday.

The latest developments came as troops who overthrew Malian President President Amadou Toumani Toure on March 22, saying they had not been given the means to combat the insurgency, face sanctions from ECOWAS.

"We wish to avoid war," Ouattara stressed. "If legitimacy is restored and these armed movement see that there is regional and international mobilisation they will leave Kidal immediately."

He added, "We must preserve Mali's territorial integrity at all costs ... we must succeed because if Mali is divided, carved up, it is a bad example."