Ecuador President Lucio Gutierrez is said to have abandoned the presidential palace after Congress voted to sack him and the army withdrew its support.
Opponents have accused Mr Gutierrez of acting like a dictator
Deputies voted unanimously to replace Mr Gutierrez with Vice-President Alfredo Palacio, in a motion accusing the president of "abandoning his post".
Mr Gutierrez left the presidential palace by helicopter, but his spokesman said he was still in his post.
Mr Gutierrez sparked protests when he tried to overhaul the Supreme Court.
There were loud cheers from the nearby public square as Mr Gutierrez climbed into a helicopter that had landed on the presidential palace.
His destination was unknown, but a spokesman for Mr Gutierrez told the BBC he would remain in Ecuador at a private house.
The armed forces took control of Quito's international airport in case Mr Gutierrez tried to leave. The chief prosecutor has issued a warrant for his arrest.
Anti-government protests have been spreading
Mr Palacio has already taken an oath of office.
The BBC's South America correspondent Elliott Gotkine says it seems Mr Gutierrez was left with little choice but to accept his fate.
Earlier, the military stepped up security across Quito, amid signs that a week of mass demonstrations were turning violent.
Some anti-government protesters clashed with supporters of Mr Gutierrez, who had arrived in the city.
Fresh protests broke out on Wednesday after a night of demonstrations in which tens of thousands of Mr Gutierrez's opponents marched on the palace.
The chief of police, Jorge Poveda, has resigned, saying he could not continue to serve while "Ecuadorian people fight among themselves".
Demonstrations have also been taking place in Guayaquil, Ecuador's largest city, as well as in the cities of Machala on the Pacific coast and Cuenca and Riobamba in the Andean highlands.
Mr Gutierrez's opponents have dubbed him a dictator, saying changes he made to the Supreme Court were attempts to illegally control the judiciary and legislation.
Mr Gutierrez has repeatedly refused to resign, saying he planned to serve out his term in office until January 2007.
The trouble began in December, when Mr Gutierrez sacked almost all of the Supreme Court judges, alleging they were biased against him.
Armed police had been deployed to protect the presidential palace
The new court promptly dropped outstanding corruption charges against one of Mr Gutierrez's allies, former President Abdala Bucaram. Mr Bucaram's Roldosista Party had backed Mr Gutierrez's drive to replace the Supreme Court.
The party also helped to block an opposition attempt to impeach Mr Gutierrez in November.