Kiev, Ukraine - Russian leaders expressed their distrust and dislike of Ukraine's new government on Monday, saying it came to power through "armed mutiny," just hours after the authorities here announced a nationwide manhunt for ousted president Viktor Yanukovych on charges of "mass murder of peaceful civilians."

Russia questioned the legitimacy of Ukraine's interim leadership, charging that it used a peace deal brokered by Europe to make a power grab and to suppress dissent in Russian-speaking regions through "terrorist methods."

The tone was much harsher than any previous Russian response to the events of the past few days. "If you consider Kalashnikov-toting people in black masks who are roaming Kiev to be a government, then it will be hard for us to work with that government," Russian Prime Minister Dmitry Medvedev said Monday.

Ukrainian lawmakers, now largely foes of Yanukovych, were defiant. Asked about Russia's displeasure, parliament member Yuriy Derevyanko said: "They can take it or leave it. It's not their business."

The search for Yanukovych was backed up by warrants authorizing the arrest of the ousted leader and 50 members of his government for their roles in the deaths of 88 Ukrainians killed by riot police and in street clashes over the past week, said Arsen Avakov, the interim interior minister.

Ukrainian officials said Yanukovych has used helicopters and ground vehicles to travel from his palatial estate outside Kiev to Kharkiv in the east, and then on to an airport in Donetsk, where border guards stopped two chartered jets from leaving the country. Some suspect that he may have moved on to Ukraine's Crimea region, which has a strong Russian-speaking majority.

Ukraine's parliament was rushing ahead to form a caretaker government and appoint a new prime minister. The move is crucial to help the country continue to meet its financial obligations and, most important, to borrow money.

The legislative body has called for a presidential election May 25, and it declared Monday that candidates can announce themselves and begin their campaigns today.

Protesters in Independence Square in central Kiev began to return home. The capital city was sunny and peaceful, with offices and businesses open again, and traffic normal.

Visitors to Yanukovych's presidential website were greeted with an "error" message. Journalists poring over documents left behind at Yanukovych's mansion found lists of expenses, including one citing a $2.3 million bill for the decoration of a dining hall and tea room.

Catherine Ashton, the European Union's top diplomat, arrived in Kiev on Monday, and U.S. Treasury Secretary Jack Lew held a phone conversation with Arseniy Yatsenyuk, a leader of the protests. But Medvedev, the Russian premier, heaped scorn on the West for what he called its "aberration of consciousness" for endorsing the toppling of Yanukovych's democratically elected government.

At the same time, Russia's Foreign Ministry spoke out in defense of members of Ukraine's Russian-speaking minority, who live primarily in the eastern and southern parts of the country.

A statement on the ministry's website warned of attempts to "nearly ban" the Russian language, purge Yanukovych loyalists from the ranks of government, stifle the press and permit neo-Nazi propaganda. It accused Ukraine's new leaders of launching a "dictatorial, and sometimes even terrorist," campaign against Russian speakers.

Similarly hostile rhetoric was voiced by Mikhail Dobkin, governor of the eastern region around Kharkiv, where many Ukrainians speak Russian as their first language. He denounced the "fascism" of the new authorities in Kiev.

At the same time, Dobkin announced that he would run for president in the May election-a sign that, however dismayed, he is prepared to play by the new rules and enter the electoral fray.

The Ukrainian parliament passed a law Monday downgrading the status of Russian as an official second language, and there were calls for the ouster of Yanukovych's allies, but Russia did not provide evidence to support its other charges.

The Ukrainian Foreign Ministry said Russia has nothing to worry about. Threats to Russian citizens "are ungrounded because the situation is stable and under control," the ministry's press secretary, Yevhen Perebiynis, told the news agency Interfax.

Russia has recalled its ambassador to Ukraine. On Monday, its sanitary service - notorious for discovering health problems with imports from countries that Russia is having a spat with - announced that it was prepared to ban foodstuffs from Ukraine on the grounds that the turmoil here could have led to lapsed standards.

The Russian denunciations have stoked fears that Moscow is encouraging a breakup of Ukraine, but such a drastic move seems distant.

Tetiana Maliarenko, a professor at Donetsk State University of Management, in Yanukovych's industrial home town in eastern Ukraine, called threats of a split, or a division into separate federated republics, an attempt to blackmail Ukraine's new leaders and said such a partition was not a serious possibility.

"I am confident it will not split in the near future," she said. "There is public support for separatism, here and in the Crimea, and separatism was always on the table, but at the same time there is no project for a future independent state and no strong leaders to do this. There is a Russian-led movement, but there is no one who can do it."