Russian Prime Minister Vladimir Putin has been appointed acting president, after President Boris Yeltsin's shock resignation on live television on Friday.

Mr Putin' appointment took effect immediately and he will now serve as acting president until elections are held on 26 March, three months earlier than planned.

"There will be no power vacuum even for a moment," said Mr Putin, in a New Year's address already broadcast in Russia's Far East.

"I want to warn that any attempt to exceed the limits of law and the Russian constitution will be decisively crushed.

"Freedom of speech, freedom of conscience, freedom of mass media, property rights - all those basic elements of a civilised society will be safely protected by the state," Mr Putin said

Earlier, President Yeltsin assured US President Bill Clinton in a 20-minute telephone call that Russia would remain committed to democracy, open markets, arms control and its constitution.

Limited powers

Pending the election, Mr Putin - as acting president - will not be able to disband parliament, call a nationwide referendum or introduce constitutional amendments, rights normally enjoyed by the Russian president.

He is not required to name a new prime minister, and has indicated he will continue in that post, at least until the first session of the newly elected lower chamber of parliament, the State Duma, planned for 18 January.

Guarantees

Earlier, Mr Putin signed a decree offering Yeltsin immunity from legal prosecution.

"He cannot be liable to legal or administrative responsibility, detained or arrested, his premises cannot be searched, he cannot be interrogated or subjected to a body search," the decree read.

The issue of whether a departing Russian president should receive legal protection from prosecution on political grounds has been a matter of considerable debate in Russian society.

President Yeltsin has been hit by corruption allegations in recent months and has reportedly been looking for assurances for the safety of himself and his family when he steps down.

Nuclear codes

President Yeltsin has handed over the "nuclear briefcase", which contains the codes controlling Russia nuclear weapons, to Mr Putin.

US President Bill Clinton was notified about President Yeltsin's move before dawn broke in Washington.

President Clinton saluted Russia's movement to democracy under President Yeltsin and pledged to work with the Russian people, Yeltsin's successor Vladimir Putin, and the winner of next year's presidential election.

Endorsement

President Yeltsin's announcement was unexpected because the 68-year old had repeatedly said he would serve out his full term, although poor health had led to increasing doubts about his ability to fulfil that promise.

"I am going. I am going earlier than my established time," President Yeltsin said in a broadcast on state-owned ORT television.

He said Russia needed to go into the new century with new political leaders.

It was announced that Mr Yeltsin will still make a visit to Jerusalem and on 5 January, a trip time to coincide with the Orthodox Christmas.

He made a clear endorsement of Mr Putin, who had already announced he would be a candidate in the 2000 elections.

"To cling to power for another six months when the country has a strong person worthy of becoming president - why should I stand in his way? Why should I wait? It's not in my character," President Yeltsin said.

A former KGB officer who only became prime minister in August, Mr Putin is widely seen as the most popular politician in Russia, with around 60% of voters saying they would back him, according to opinion polls.

His strong handling of the war in Chechnya and no-nonsense manner has appealed to many Russians, who want strong leadership to tackle their country's enormous economic, political and social problems.

Apology

President Yeltsin chose a particularly significant day for his bombshell in a country where New Year is far more widely marked than Christmas.

He has presided over eight turbulent and often chaotic years of social and political transformation in Russia, which have seen the living standards of many people worsen.

During his address he appealed to Russians to forgive him for what he said had been the errors of his administration.

"I want to beg forgiveness for your dreams that never came true. And also I would like to beg forgiveness not to have justified your hopes," the president said.

The Russian public seemed stunned by the suddenness of the news.

"At first I though it was a New Year's Eve joke. I thought it could not be true," said Yelena Vasilyevna, a retired electrical engineer.

"His health must have let him down," she said.

"The Kremlin has already decided that Putin is the new president," said one Moscow taxi driver. "So, what do we care if he turns into one now?"