As Moscow lashed out Thursday at Ukraine’s new leaders and the Western nations it believes to be backing them, ousted president Viktor Yanukovych resurfaced in Russia and claimed he is still Ukraine’s legitimate head of state.

Yanukovych, now apparently under Russia’s protection, hadn’t been heard from since he fled Kiev on Saturday. He argued in a statement distributed Thursday that his opponents had reneged on a power-sharing deal they had signed with him last Friday. The Russian government, which had refused to endorse the deal at the time, now says it agrees with him and wants the terms of the agreement to be reinstated.

There is little chance of that happening, and Moscow knows it.

But it gives the government of President Vladimir Putin a justification for its refusal to have any dealings with the new authorities in Kiev, which is under immense strain from pro-Russia protests on the Crimean Peninsula, a collapsing currency, coffers left empty by Yanukovych and uncertain control of the country.

The new leaders are also facing a major Russian military exercise on their doorstep. And they must contend with militant groups on the Maidan — the protest site in Kiev that is also known as Independence Square — who see them as being too likely to betray the uprising.

Ukraine in crisis

On his first day on the job, the interim prime minister, Arseniy Yatsenyuk, said he and his cabinet ministers were going to have to take a “kamikaze” approach — immediate and very painful steps — to stem a financial meltdown.

They have also applied for help from the European Union and the International Monetary Fund.

“Pensions have not been paid in full for more than a month,” Yatsenyuk told the Ukrainian parliament, called the Verkhovna Rada. “The foreign currency and gold reserves have been ransacked. And we are doing everything we can today to stop the situation from deteriorating further.”

Yanukovych had secured a $15 billion bailout from Russia late last year, in exchange for turning his back on the European Union, but Russia has since suspended the program after committing — and now writing off — $3 billion.

Ukraine’s new government said Thursday that Yanukovych and his allies had spirited $70 billion out of the country illegally since his election to the presidency in 2010.

Under the terms of last week’s short-lived deal, brokered by Poland, Germany and France, Yanukovych was to have remained in power until new presidential elections could be held in December. And a “national unity” government was to be formed with members from all the major parties.

But Yanukovych absconded hours later, and the parliament voted shortly afterward to remove him from office. He has since been charged with “mass murder” in connection with the deaths of nearly 90 people during the protests. The government installed Thursday draws only from what had been the opposition parties — and this is a factor that Moscow especially objects to.

“The obligation to set up a national unity government sank into oblivion,” the Russian Foreign Ministry said on its Web site. “Instead, as was announced in Maidan, ‘a government of winners’ has been set up that includes representatives of nationalist extremists.”

Yanukovych’s Party of Regions, which is now the opposition, has repudiated him. But he said in his statement Thursday that this was done under duress.

“I officially declare my determination to fight until the end for the implementation of the important compromise agreements concerning the Ukrainian recovery from the profound political crisis,” Yanukovych said.

Ukraine has put him on an international wanted list and hopes to send him to the International Criminal Court at The Hague for a trial. A new vice prime minister, Vitaly Yarema, told the news service RBC-Ukraine that the government would seek Yanukovych’s extradition from Russia.

“He is no longer president; he is a wanted person who is suspected of mass murder, a crime against humanity,” Yatsenyuk said.

Russia will almost certainly not send Yanukovych back to Kiev as long as it considers the new government there to be illegitimate. But that doesn’t mean that Moscow wants to return him to power, said Dmitri Trenin of the Carnegie Moscow Center.

“The Kremlin has given up on him,” Trenin said. “He is not worthy of being seen as a serious player in Ukraine.”

A Russian newspaper and a Ukrainian Web site reported that Yanukovych had been spotted Tuesday evening in Moscow — at the aptly named Ukraine Hotel.

Russian news agencies reported that Yanukovych plans to hold a news conference Friday afternoon in the Russian city of Rostov-­on-Don, about 40 miles from the Ukrainian border as the crow flies and close to his home base of Donetsk.

Interfax and Itar-Tass both reported that the Moscow government has provided Yanu­kovych with a security guarantee as long as he is on Russian soil.

However, there has been no indication whether this pledge of protection could lead to permanent asylum. A Russian lawyer told the Komsomolskaya Pravda newspaper that if Yanukovych were formally accused of murder, Russia should extradite him.

“Based on the norms of international law and signed mutual treaties,” Alexander Treshev said, “Russia would have to do it.”

Ignoring such obligations would damage Russia’s image, he said.

William J. Burns, U.S. deputy secretary of state, was in Kiev on Wednesday and Thursday conferring with political leaders and discussing financial help.

“The United States stands with the Ukrainian people at this remarkable moment,” he said, according to the State Department Web site, “and we will do all we can to help them build the strong, sovereign and democratic country they so richly deserve.”

Such comments have drawn criticism from Moscow, which believes the United States and other Western nations have inappropriately chosen sides in Ukraine.

“Russia urges West to realize responsibility for Ukraine’s failed peace deal,” the Foreign Ministry tweeted Thursday. “Russia advises everyone to give up provocative statements on Ukraine.”

Thursday was the first full day of large military preparedness drills in western Russia, which will involve 150,000 troops. Russia has notified NATO that the exercises are not related to Ukraine.

Nevertheless, Trenin said, they show that “Russia is prepared to defend its interests in this part of the world.”

Kathy Lally in Moscow contributed to this report.