President Vladimir Putin abruptly fired his prime minister and the rest of the cabinet on Tuesday in a surprise pre-election shake-up that removed the most powerful ally of big business remaining in the Russian government.

The dismissal culminated years of quiet tension between Putin and the prime minister, Mikhail Kasyanov, and allowed the president to clear out the remnants of predecessor Boris Yeltsin's team as he prepares to build his own second-term government. While appearing largely loyal in public, Kasyanov had broken with Putin recently over the government's pursuit of oil tycoons.

Putin's move shocked even senior cabinet members, who learned about it from television, and led to uncertainty about how he intends to reshape the government. Under the constitution, Putin must now nominate a new prime minister by March 9, just five days before a presidential election he appears certain to win. His choice may indicate whether he is siding with pro-Western economic reformers or his fellow KGB veterans who want to reassert the state's role in society.

Putin installed Deputy Prime Minister Viktor Khristenko as acting prime minister. Khristenko, 46, an economic technocrat from the Siberian city of Chelyabinsk, came to Moscow under the patronage of Anatoly Chubais, then the deputy prime minister and the architect of Russia's privatization in the 1990s.

"This decision is not related to an evaluation of the activities of the previous government, which on the whole I consider satisfactory," Putin said in an unannounced appearance on state television. "This decision was due to my desire to outline once again my position regarding the country's course of development after March 14."

But analysts and critics said Putin created more confusion than clarity, reflecting the ongoing debate inside the Kremlin. Unlike Yeltsin, who seemed to shed prime ministers with each passing season, Putin had not reshuffled the top echelon of government since taking power in 2000 and prided himself on a predictable stability.

"The fact that Putin has resorted to the typically Yeltsin-like gesture of firing the government without explanation only tells us about serious uncertainty in the Kremlin," said Lilia Shevtsova, a scholar at the Carnegie Moscow Center. "Putin creates so many questions and puzzles that he has no answer to them."

Leonid Gozman, a Chubais aide, said the dismissal was unjustified because "there is no crisis in the country." Yet he said it would force Putin to tip his hand. "The answer will be very clear in a week when he says who will be my prime minister. If it's a liberal person, it's one answer. If it's a very conservative person with a negative attitude toward reforms and relations with the West, it's another answer."

In separate interviews, two political consultants with ties to the Kremlin, Sergei Markov and Vyacheslav Nikonov, identified the same four candidates for Kasyanov's replacement: Khristenko, Finance Minister Alexei Kudrin, Deputy Prime Minister Boris Alyoshin and Deputy Kremlin Chief of Staff Igor Shuvalov. Putin should have no trouble securing confirmation for his choice, because his party won control of the State Duma, the lower house of parliament, in December elections.

Some analysts assume Khristenko has the inside track for the country's second-ranking position, responsible primarily for domestic affairs. "It's hard to imagine Khristenko was made acting prime minister and he's going to be dumped in a week," said Al Breach, chief economist at Brunswick UBS brokerage here. "Why nominate Khristenko just for a couple of days?"

Some former colleagues say he would be a competent but pliable choice by a president unwilling to allow commanding figures around him. "Khristenko is a weak kind of person, so he will be easier to influence," said Mikhail Delyagin, a former adviser to Kasyanov. "I don't think Khristenko will be seen standing up for business under any circumstances."

Many others, though, consider Khristenko a short-term caretaker. Democratic reformers fear that Putin may pick Defense Minister Sergei Ivanov, another former KGB officer and favorite of the siloviki, or men of power, from the military and secret services. Ivanov would offer a less friendly face to the West, having opposed the U.S. military presence in Central Asia following the Sept. 11, 2001, terrorist attacks. As the government took on the Yukos oil company, Ivanov talked about the state reclaiming control of Russia's natural resources.

Kasyanov long resisted such moves and criticized what he called heavy-handed attacks on Yukos and its chief shareholder, Mikhail Khodorkovsky, who was arrested at gunpoint in Siberia on Oct. 25 on charges of tax evasion and fraud. The Khodorkovsky case prompted Kremlin Chief of Staff Alexander Voloshin, the other holdover from the Yeltsin clan known as "the Family," to resign Oct. 30. Delyagin said Kasyanov came close to being fired as well.

Since then, though, Kasyanov harbored hope he could survive, suggesting in an interview in January that he might remain in a second Putin term. Since Putin first promoted him from finance minister in May 2000, Kasyanov, 46, had constantly been rumored to be on the way out, yet somehow had managed to hang on. He presided over a boom in which Russia's economy expanded by 38 percent, but opinion polls showed he was unpopular with voters, who blamed him for government inertia and corruption.

Under the constitution, Putin would have had to dismiss the cabinet after the May inauguration anyway. But instead of taking the face-saving way of removing Kasyanov, Putin chose the more confrontational route.

Markov, the Kremlin-linked consultant, said Kasyanov "had been too close to certain oligarchs," referring to such tycoons as Khodorkovsky. "He was a successful prime minister because there was economic growth, but he was a prime minister whose time was over."

Nikonov, the other consultant, said the dismissal was meant to energize a lackluster campaign and tell the electorate that Putin was "speeding up the reforms and making the government more energetic."

Putin's move came the same day four other presidential candidates said they might withdraw because the election system was so heavily tilted in his favor.

"The presidential election campaign in Russia is increasingly developing features of lawlessness and falsehood," said Irina Khakamada, the most prominent democratic reformer in the race. "In this situation, the competition of ideas and alternatives is becoming impossible."

Similar grievances were issued by Sergei Glazyev, a former Communist who co-founded a nationalist political party last year; Nikolai Kharitonov, the Communist standard-bearer; and Ivan Rybkin, a former parliament speaker who has accused Putin of "state crimes" and has fled the country for fear of retribution.

Prime Minister Mikhail Kasyanov, left, had differed with President Valdimir Putin over the government's legal pursuit of oil tycoons.