Russian president Vladimir Putin announces re-election bid

"I couldn't find a better place and moment for that," he said, to massive applause.

"Thank you for your support, I will run for president."

Mr Putin has been in power in Russia since 2000.

He served two presidential terms in 2000-2008, then shifted into the prime minister's seat because of term limits, but continued calling the shots while his ally, Dmitry Medvedev, served as placeholder president.

Mr Medvedev had the presidential term extended to six years and then stepped down to let Mr Putin reclaim the presidency in 2012.

While few doubted that Mr Putin would run in the March 18 vote, a delay in announcing his bid was seen as part of the Kremlin's political manoeuvring.

Mr Putin's approval ratings top 80%, making him certain to win an easy first-round victory.

Blue-collar workers and state employees form the core of his support base.

"Thank you for your work, for your attitude to your jobs, your factory, your city and your country," Mr Putin told workers. "I'm sure that together we will succeed."

Just hours earlier, Mr Putin was asked about his intentions at a meeting with young volunteers in Moscow.

He said he would decide shortly if he would seek another six-year term.

The upper house of parliament is expected to give the formal start to the election campaign later this month.

The veterans of past campaigns - Communist chief Gennady Zyuganov, ultranationalist Vladimir Zhirinovsky and liberal leader Grigory Yavlinsky - have all declared their intention to run.

They are likely to be joined by Ksenia Sobchak, a star TV host who is the daughter of late former St Petersburg mayor Anatoly Sobchak, who was Mr Putin's boss in the 1990s.

The most visible Putin foe, Alexei Navalny, also wants to run, even though a conviction he calls politically motivated bars him from joining the campaign.

He has organised a grassroots campaign and staged rallies across Russia to raise pressure on the Kremlin to let him register for the race.

AP