In an emergency meeting, the parliament on Thursday installed opposition leaders as acting president and prime minister and gave them until Friday to present a new government for the Central Asian country.
Thursday's protests were a culmination of days of demonstrations against what the opposition say were rigged parliamentary elections and years of poverty and corruption.
Security forces at first repelled protesters trying to enter the heavily defended White House - the seat of government - but then withdrew, allowing thousands to stream into the building and take control.
One protester could be seen waving a flag from the second floor of the White House. Above, another protester tossed documents out to the cheering crowd of thousands below. The square nearby was splattered with blood.
"This is a popular revolution and the power is in the hands of the people, we don't fear anyone any more," Askat Dukenbayev, a professor from the local American University, said.
Celebrations have spiralled into
anarchy in capital Bishkek
More than 70 people were reported injured in clashes with pro-Akayev supporters in Bishkek, a city of 800,000.
The United States called for calm and for fresh elections to be held.
Rumours flew that Akayev had fled the mountainous country, which appears likely to become the third former Soviet state in two years to see its entrenched leadership fall to popular protest after disputed elections, following Ukraine and Georgia.
Separately, Prime Minister Nikolai Tanayev tendered his resignation, an opposition spokesman said.
Most of Kyrgyzstan's opposition leaders are former political allies of Akayev who fell out with him for one reason or another.
Parliament appointed the head of the opposition coordinating committee, Kurmanbek Bakiev, as acting prime minister and gave him until 0500 GMT on Friday to come up with candidates for ministerial positions.
President Akayev is thought to
have fled the country
Kyrgyzstan Supreme Court head Kurmanbek Osmonov was quoted by Russia's Itar-Tass news agency as saying the court had annulled an electoral commission decision validating the parliamentary polls.
The ruling opens up the possibility of fresh elections.
Felix Kulov - one of the opposition leaders freed from jail on Thursday by protesters - denied media reports that quoted him as saying Akayev had resigned after 14 years in office.
Kulov, 55, a former police chief and once head of the secret services, failed in a bid to become president in elections in 2000. He was appointed interior minister on Thursday.
Acting president Ishenbai Kadyrbekov - a former construction minister - had been disqualified from running in the disputed parliamentary election, which international observers had also declared to be flawed.
With no police on the streets of Bishkek, looters, mainly young men, ransacked department stores and casinos, emptied jewellers' shops and made off with cars. Thick smoke filled the night air after mobs torched stores.
"There are no police anywhere in the city," an emergency services spokesman said.
|Protests against President Akayev |
forced his government to crumble
Parliament gave Kulov special powers to clamp down on the lawlessness in Bishkek.
"We will establish order. We will not allow looting. We will hold our own elections to start our rule," Bakiev, who was prime minister from 2001 to 2002, said.
Kyrgyzstan, a mainly Muslim country of five million bordering China, lies in an energy-rich region where Washington and Moscow vie for influence. Each has a military base outside Bishkek.
There was speculation Akayev might have flown to neighbouring Kazakhstan or had sought sanctuary in a Russian airbase outside the capital.
The opposition had taken control earlier this week of Osh and Jalalabad - two key towns in Kyrgyzstan's poorer south, scene of bloody ethnic conflict in the dying days of the Soviet Union, where resentment is strong against the richer north.