He said Yanukovych had then fled in an unknown direction, traveling by car with a diminished security detail.
The pursuit of Yanukovych, a man now widely despised even by many of his former supporters, gripped the nation Monday, as the parliament continued its efforts to rebuild the government, with hopes of appointing an acting prime minister and having the rest of a provisional government Tuesday.
With former Prime Minister Yulia V. Tymoshenko, freed from prison on Saturday, saying she did not want to be considered for the post, speculation on the premiership focused on her ally, Arseniy P. Yatsenyuk, who has been a leader of the anti-Yanukovych protests since they began in late November.
Western officials on Monday continued to praise the developments in Ukraine saying that parliament had successfully filled a power vacuum, and that democratic institutions had functioned successfully. Russia, however, stepped up its criticism after recalling its ambassador from Kiev, the capital, on Sunday.
"Today, I see no legitimate Ukrainian partners for dialogue," the Russian prime minister, Dmitry Medvedev, said in Sochi, Russia, a day after the close of the Winter Olympics, according to the Interfax news service. "If people crossing Kiev in black masks with Kalashnikov rifles are considered a government, it will be difficult for us to work with such a government."
In fact, the security situation in the Ukrainian capital seemed to improve Monday, with regular law enforcement bodies and some anti-government fighters sharing responsibility for guarding government buildings and directing traffic. A sense of workaday calm seemed to return to the city, even as barricades still surrounded the main protest sites.
As Yanukovych's public persona morphed from feared strongman to detested fugitive, any last vestiges of support for him seemed to vanish even in the pro-Russia eastern and southern parts of the country, which had historically provided his base of political support.
Yanukovych's Party of Regions, which had supported him until lawmakers began defecting over last week's mass killings in Kiev, issued a statement Sunday saying the country had been deceived, robbed and betrayed. "All responsibility for this lies with Yanukovych," the party wrote. "We condemn the flight and cowardice of Yanukovych. We condemn the betrayal."
Yanukovych and his family were known to have accumulated vast wealth during his time in office, and he was believed to have access to at least one yacht that might ferry him out of Ukraine.
On Facebook, Avakov said that after abandoning his residence near the capital, Yanukovych had flown by helicopter to Kharkiv in eastern Ukraine, where he prepared a video statement on Saturday declaring that he remained president. Then, he went to the airport in Donetsk, where he and several companions sought to flee the country on Falcon airplanes.
Border police at the airport prevented the planes from flying, Avakov said, and Yanukovych then departed in a motorcade for the south. After learning that parliament had voted to strip him of power, Yanukovych began avoiding government residences, including a presidential country house in Crimea where he was expected to seek shelter.
In addition to the murder charges, there have been calls for prosecution of Yanukovych on corruption charges after the discovery of astonishing trappings of wealth at his abandoned presidential residence in a national park outside of Kiev. Throughout the weekend, curious and angry members of the public streamed to the compound to gawk at the collections of expensive modern and antique cars, the private zoo and other gauche accouterments.
As journalists scoured the compound, sorting through a trove of documents that had been partly burned or dumped in a river, local news media began reporting allegations of embezzlement and corruption, and new details about Yanukovych's personal life emerged.
The Kyiv Post, a newspaper here, said it had found evidence that Yanukovych, 63, was living at the residence with a 39-year-old girlfriend and her 12-year-old daughter from a prior relationship. Yanukovych has been married for 42 years, but his wife, Lyudmila, has long lived in Donetsk and typically has not performed the duties of first lady.
It was not clear whether the girlfriend, identified as Lyubov Plezhay, was traveling with Yanukovych. Avakov said the ousted president was accompanied by Andriy Klyuyev, a close political ally whom he had recently named as chief of the presidential administration.