The acting interior minister - appointed by parliament when Yanukovich fled at the weekend after mass protests sparked by his rejection of closer ties with the European Union - said the 63-year-old was now on the wanted list and had last been seen at Balaclava in Crimea, near Russia's Sevastopol naval base.
"An official case for the mass murder of peaceful citizens has been opened," Arsen Avakov wrote on Facebook, referring to the shooting by police marksmen of many of the 82 people killed in two days of bloodshed in Kyiv last week.
"Yanukovich and other people responsible for this have been declared wanted," he added.
The ousted president was still at large, Avakov said. He had left by helicopter on Friday from Kyiv, where his lavish residence was quickly overwhelmed by curious compatriots who took its lavish fittings as proof of grandiose corruption.
According to a leaked document published online, Yanukovich drew up plans to use thousands of troops to crush the protests that eventually toppled him.
Ukrainian journalists are going through thousands of papers they say were found near Yanukovich's opulent residence near Kyiv after he fled the capital and some documents have already started to surface in the Internet.
Although its authenticity could not be confirmed, parliamentary deputy Hennadi Moskal, a former deputy interior minister, published a document online detailing a plan to surround Independence Square - the cradle of the uprising - with snipers and open fire on the protesters below.
Armoured vehicles and about 22,000 police would have been involved, including about 2,000 Berkut riot police, if it had been fully enacted, the document showed.
Moskal, a member of former prime minister Yulia Tymoshenko's Batkivshchyna party, said he had published the document to put pressure on Ukraine's new authorities to bring Yanukovich to justice.
Russia doubts legitimacy of current authorities
Russian Prime Minister Dmitry Medvedev said yesterday his country had grave doubts about the legitimacy of those in power in Ukraine following Yanukovich's ouster, saying their recognition by some states was an "aberration".
"We do not understand what is going on there. There is a real threat to our interests and to the lives of our citizens," Medvedev was quoted by Russian news agencies as saying.
"There are big doubts about the legitimacy of a whole series of organs of power that are now functioning there."
"If people crossing Kiev in black masks and Kalashnikov rifles are considered a government, it will be difficult for us to work with such a government," Medvedev said.
The Russian President apparently referred to the extreme-right forces which according to some reports have had a “leading role”, or at least have been the most radical and violent force in the Maidan protests.
Moscow said it would not deal with those who led an "armed mutiny" against Yanukovich, and said it now feared for the lives of its citizens, notably in the Russian-speaking east and Crimea on the Black Sea.
Russia cited a duty to protect the lives of its citizens in 2008 as one justification for military intervention in Georgia, another former Soviet republic, in support of Kremlin-backed separatists in South Ossetia.
Ukraine heading for bankruptcy?
While Russia, its strategy for maintaining influence in its former Soviet neighbour in shreds, made clear its $15-billion (€11 billion) package of loans and cheap gas deals was in jeopardy, the European Union and United States offered urgent financial assistance for a new government that may be formed today.
They were responding to warnings from Ukraine's acting head of state Olexander Turchinov that the country was heading for bankruptcy.
However, both the EU and the USA indicated that any comprehensive package was likely to take shape only after elections in May and in coordination with the International Monetary Fund, which is likely to demand painful economic reforms.
Turchinov, appointed after Yanukovich was stripped of his powers by parliament on Saturday, sounded the alarm about the economy in an address to the nation on Sunday evening.
"Against the background of global economic recovery, the Ukrainian economy is heading into the abyss and is in a pre-default state," he said.
Financial analysts said, however, that the economy was not about to collapse. Prices of its government bonds rallied and the cost of insuring its debt fell, in a sign of investors' confidence that it could avoid default.
The European Commission confirmed a variety of options were being discussed. "The EU has been working on an international economic support package for Ukraine - short, medium and long-term support to address the challenges of the Ukrainian economy," said Commission spokesman Olivier Bailly.
Ukraine’s Finance Ministry said it needed $35 billion (€25.5 billion) in foreign assistance over the next two years and appealed for urgent aid in the next one or two weeks. It called for a donors' conference involving representatives of the European Union, the United States and the International Monetary Fund.
EU officials said it was highly unlikely Europe, the United States or anyone else would put the kind of sums mentioned by Kiev on the table right away. However, smaller bilateral loans, possibly coordinated by the EU, could be used to give short-term help, they added.
Discussions have already taken place with Japan, China, Canada, Turkey and the United States on possible help, a senior European Commission official said, and efforts are being made to keep Russia engaged in the process as well.
European Union foreign policy chief Catherine Ashton was in Kyiv on Monday to discuss measures to shore up the ailing economy, which the finance ministry said needs urgent financial assistance to avoid default.
After her talks with Turchinov, she was quoted in a statement from the Ukrainian parliament as saying: "We are ready to support Ukraine and give a signal to other countries that your country is not only solving the problems of the past but also looking ahead."
EU officials have said that an Association Agreement (AA), coupled with a Deep and Comprehensive Free Trade Agreement (DCFTA), spurned by Yanukovich in November under pressure from Moscow, could be available to Ukraine once it has a government to negotiate.
Whoever takes charge in Kyiv - possible prime ministers include Tymoshenko ally Arseny Yatsenyuk and billionaire former minister Petro Poroshenko - faces a huge challenge to satisfy popular expectations and will find an economy in deep crisis.