Vladimir Putin faces new protests Monday to challenge his victory in a presidential election he said had prevented Russia from falling into the hands of enemies trying to usurp power.
Putin's opponents, complaining of widespread fraud in Sunday's election, said they did not recognize the results and would rally near the Kremlin at 7 p.m. (1500 GMT).
But the former KGB spy, who after four years as prime minister will be returning to the post he held from 2000 until 2008, said with tears rolling down his cheeks that he had won a clean victory.
I promised you we would win. We have won. Glory to Russia, Putin, dressed in an anorak and flanked by outgoing President Dmitry Medvedev, told tens of thousands of flag-waving supporters Sunday night under the Kremlin's red walls.
Denouncing attempts to destroy Russia's statehood and usurp power, he said: The Russian people have shown today that such scenarios will not succeed in our land ... They shall not pass!
Putin, 59, is on collision course with the mainly middle-class protesters who have staged rallies in the capital and other big cities since a disputed parliamentary poll on December 4.
The protest organisers, who see Putin as an autocratic leader whose return to power will stymie hope of economic and political reforms, said their demonstrations would now grow.
He is forcing things to breaking point. He is declaring war on us. As a result the base of aversion to him is growing, said journalist Sergei Parkhomenko, one of the leaders of the opposition protest movement.
DECLARATION OF WAR
Partial results, with nearly 100 percent of the votes counted, put Putin on almost 64 percent of the votes.
His nearest rival, Communist Party leader Gennady Zyuganov, was on about 17 percent of votes, and nationalist Vladimir Zhirinovsky, former parliamentary speaker Sergei Mironov and billionaire Mikhail Prokhorov were below 10 percent, although Prokhorov won plaudits for his campaign.
Zyuganov said his party would not recognize the result and called the election illegitimate, dishonest and not transparent. Liberal leader Vladimir Ryzhkov also said it was not legitimate.
Despite the opposition, mainly among well-educated and relatively well-off young professionals, Putin's support remains high in the provinces and his victory had not been in doubt.
The initial challenge for the man credited by many Russians with rebuilding the country's image and overseeing an economic boom in his first presidency, had been to win more than half the votes Sunday and avoid a second-round runoff.
His clear victory will enable him to portray his return to the presidency as a strong sign of public support against the protesters, whom he has portrayed as a destabilising minority and pawns of foreign governments.
But the mood has shifted in the country of 143 million and the urban protest movement portrays him as an obstacle to change and the guardian of a corrupt system of power.
Putin, who will be inaugurated in May, is likely to revert to the fighting talk against the West that was the hallmark of his first presidency and his election campaign.
Economists say a key test of Putin's return will be how far he is ready to go to reform an economy heavily dependent on energy exports, and caution that his populist campaign spending promises could return to haunt him.
It's a watershed - Russia faces decline and stagnation unless they really kick-start reforms, and push forward an ambitious reform agenda, said Tim Ash, head of emerging markets research at Royal Bank of Scotland in London.
An international observer mission was due to announce its findings at 2 p.m. (10 a.m. British time) and thousands of people took part as voluntary monitors to try to prevent fraud.
Golos, an independent monitoring group, said it had registered at least 3,100 reports of violations nationwide.
(editing by Elizabeth Piper)