Rebel forces in Chad are said to be on the outskirts of the capital as they launch an offensive to overthrow the president.
Columns of fighters from the United Front for Democratic Change, or FUC, reportedly made swift progress as they advanced from the east.
But they are said to have faced stiff resistance from forces loyal to the government as they neared N’Djamena.
The US and United Nations have responded by evacuating non-essential personnel.
The rebels say their objective is to take over the capital before the election on May 3rd.
They accuse president Idriss Deby of being corrupt and autocratic.
Ali Kedealaye is the rebel leader. “We have to end this disorder,” he said of the current government, “We need a stable regime, for the Chadian people. We need a regime that is supported by the entire population.”
President Deby accuses neighbouring Sudan of helping the rebels, who include many defectors from the Chadian army.
Former colonial power France says it has reinforced its military contingent, and Paris has condemnded any attempt to take power by force.