Witnesses say Tuareg rebels have taken control of a key town in northeastern Mali.
The rebels entered Kidal on Friday, a day after launching an offensive on the remote town, the capital of Mali's Kidal region.
Reports from the area say the rebel MNLA was assisted by an Islamist group known as Ansar Edine.
In the capital, Bamako, the leader of last week's coup said his country needs outside help to halt the rebels and protect Mali's territorial integrity. Captain Amadou Sanogo told reporters Friday the situation is "critical."
The coup leaders are facing growing international pressure to give up power. On Thursday, the Economic Community of West African States gave the military junta three days to restore constitutional order.
However, Remi Ajebewa, a top ECOWAS official, said the regional bloc will accept a solution that does not reinstate President Amadou Toumani Toure.
"We want the military junta to understand that they cannot come to power through unconstitutional means," Ajebewa said. "And as such, they should either relinquish power or look for somebody credible right now [to rule], and then they should give us a roadmap of what they are going to do.”
Earlier in the day, a delegation of West African presidents abandoned plans to meet with the junta leaders in Mali's capital, Bamako, because of a pro-coup demonstration at the airport. The regional group instead held an emergency meeting in Ivory Coast.
President Toure was deposed last week in a coup by soldiers angry at his handling of the Tuareg rebellion in the north. Toure told French media on Wednesday that he is not in detention and remains in the country.
The rebellion began in January, a couple of months after heavily-armed Tuareg fighters returned from Libya, where they were assisting ousted Libyan leader Moammar Gadhafi.
The coup came just weeks before elections and the scheduled end of Toure's term.
Some information for this report was provided by AP and Reuters.