Mali’s junta leader promised to reinstate the Constitution from yesterday as northern rebels entered the ancient trading post of Timbuktu.

Amadou Sanogo, who led a military coup on March 22, also pledged to re-establish all state institutions before organising a transfer of power back to civilians through democratic elections.

He made the promises after the 15-nation Ecowas grouping threatened sanctions, including a crippling closure of borders around the land-locked state, if the junta did not begin handing power back by midnight.

The aim of the putsch by disgruntled soldiers was to step up the battle against the northern rebels. But the coup has backfired, emboldening the Tuareg-led rebellion to seize new ground in its quest for a northern homeland. Yesterday they entered their latest target, Timbuktu, after government forces fled.

“We are making the solemn commitment to re-establish, from today, the Malian constitution of February 25, 1992 and the institutions of the republic,” Mr Sanogo said in a statement read out at a barracks outside the capital Bamako.

Mr Sanogo, a hitherto obscure US-trained captain, said the junta had agreed to consult with local political forces to set up a transition body “with the aim of organising peaceful, free, open and democratic elections in which we will not take part”.

There was no immediate reaction from Ecowas. However, the re-establishment of the Constitution and state institutions were two measures named earlier by an envoy of Burkina Faso President Blaise Compaore, the crisis mediator, as essential preconditions for Mali to avoid sanctions.

“After that, we shall see what happens as regards the person of (Malian) President Amadou Toumani Toure,” Burkina’s Foreign Minister told Reuters by telephone minutes before Mr Sanogo’s statement. “We want to be careful, we have to go gradually,” he said, warning of the risk of a power vacuum.