Russia's presidential election will take place on March 18, the upper house of parliament said on Friday, in polls that are all but certain to return Vladimir Putin to the Kremlin for a new six-year term.
The election campaign will kick off on Monday, agencies quoted senators as saying.
"According to our calculations there are already at least 23 people who have expressed a desire to stand," said Ella Pamfilova, head of the Central Election Committee, according to Interfax.
Independent candidates are officially required to collect 300,000 signatures of support before they are allowed on the ballot paper.
Opposition leader Alexei Navalny, who has spent the last year gathering support for a Kremlin bid, is barred from running because of a criminal conviction that he says is politically motivated.
"Elections have officially been announced. All candidates should be allowed to stand. If not, we will not recognise them and will organise a voter boycott," the 41-year-old lawyer said on Twitter.
Others who have announced their candidacy include Ksenia Sobchak, a socialite turned opposition journalist who many suspect is standing as a Kremlin "spoiler" candidate to split the opposition and boost interest in the polls.
At his end-of-year press conference on Thursday, Putin said he was for political competition but did not see any realistic opponents in the forthcoming election.
"It is up to me to form the opposition myself?" he asked.
March 18 will mark four years since Putin signed a treaty that declared Crimea a part of Russia after it was annexed from Ukraine.