A leading opponent of the Akayev regime, Felix Kulov, was freed from prison and said Akayev had signed a letter of resignation, the ITAR-Tass news agency reported. Kulov said the opposition would guarantee Akayev's security "because there must be a peaceful transfer of power".
Kurmanbek Bakiyev, one of two key opposition leaders, said on opposition-controlled state television that "Akayev is no longer on the territory of Kyrgyzstan." He also said Prime Minister Nikolai Tanayev had resigned, but that the Security, Interior and Defense Ministries were working with the opposition.
The Interfax news agency, without citing sources, said Akayev had flown to Russia, but it later said he changed course for Kazakhstan and landed there. Earlier, the news agency said Akayev's family had been heading to Kazakhstan.
Members of the upper house of parliament that was in power before February's election met Thursday night to discuss keeping order in the nation and conducting a new presidential vote, perhaps as early as May or June. They elected a former opposition lawmaker, Ishenbai Kadyrbekov, as interim president.
The lower house of parliament also named prominent opposition leader Kurmanbek Bakiyev acting prime minister early Friday, a lawmaker said after the chamber held a closed-door session.
Legislator Karganbek Samakov told reporters that the lawmakers had named Bakiyev to head the interim government and would be choosing acting ministers later Friday, when they reconvene. He made no other statements, and Bakiyev left parliament without commenting.
Under Kyrgyzstan's old governmental system, most power rested with the president. It was not clear whether duties would be divided similarly under the interim system.
It was also unclear whether the decision was legally binding — in part because of uncertainty over whether Akayev had indeed stepped down.
A member of the upper house of parliament, Temir Sariyev, said "nobody knows what is legitimate right now."
Shortly after the demonstrators streamed into the government headquarters, opposition activist Ulan Shambetov sat in Akayev's chair in celebration, another demonstrator holding a Kyrgyz flag triumphantly behind him.
"It's not the opposition that has seized power, it's the people who have taken power. The people. They have been fighting for so long against corruption, against that (Akayev) family," Shambetov said.
In Washington, Secretary of State Condoleezza Rice said the upheaval in Kyrgyzstan could wind up a democratic success story if political change occurs without violence.
"This is a process that's just beginning. We know where we want to go," Rice said.