The victory of a pro-Kremlin candidate in a mayoral election in a southern Russia city was legitimate despite some confirmed violations at the polling stations, prosecutors said Tuesday.

Their ruling follows the complaints of opposition candidate, Oleg Shein, who claimed that the March 4 poll to elect the mayor of Astrakhan, a city of half a million people, was rigged, and who has since been on a hunger strike in protest.

The dispute in Astrakhan is the first major election-related dispute since Prime Minister Putin -- who was Russia's president in 2000-2008 -- was elected for a new term on March 4.

Allegations of widespread fraud in last year's parliamentary elections angered thousands of Russians and inspired Russia's largest post-Soviet street protests. Now that the protest movement seems to be waning, opposition leaders are focusing at local elections in an attempt to foster grass-roots democracy.

In the Astrakhan vote, the pro-Kremlin candidate Mikhail Stolyarov got 60 percent of the vote and Shein received 30 percent, according to the official results.

Opposition has complained that the vote was rigged, saying that election observers at many polling stations were not allowed to monitor the count and the protocols of election results handed to observers often differed from the protocols submitted to the election commission. The authorities have denied the allegations.

Shein has been on the hunger strike for 25 days to protest the result. In the photographs posted on social media he looks frail and pale.

In a reply to Shein's claims, the prosecutor's office in the Astrakhan region said Tuesday that its probe confirmed violations at some polling stations, but insisted they were not widespread and could not influence the outcome.

"The violations that were uncovered by the prosecutors during the election campaign and afterward did not present a significant breach of Oleg Shein and his representatives' election rights and could not influence the legitimacy of the vote count," the prosecutors said in a statement.

Opposition activists have seized on the dispute to highlight what they say is election fraud perpetrated by the government.

Anti-corruption campaigner Alexei Navalny, who joined some thousand people in protest in Astrakhan on Tuesday, said Shein and his supporters were trying to protect their dignity.

A video of the rally that Navalny posted online shows the crowd chant: "We are the power!"

The police dispersed the rally and detained one man who attempted to pitch up a tent on the square, Russian news agencies reported.