MOSCOW (AP) -- A large opposition faction stormed out of Russia's parliament on Wednesday to protest Vladimir Putin's refusal to look into claims of vote-rigging in a mayoral election that has sparked nationwide anger.

Putin, who returns for a third term as Russian president on May 7, told the Duma he had no authority over local elections and suggested that critics go to court instead to contest the result. His remarks prompted the entire Just Russia faction to leave the session.

Oleg Shein, a member of the Just Russia party who ran for mayor in the southern city of Astrakhan, has been on a hunger strike for 27 days to protest the results of the March 4 poll that he and other opposition figures said was marred by rampant fraud in favor of a Kremlin-backed candidate. About 20 of his supporters have joined the hunger strike.

Shein's protest has received nationwide attention, drawing support from a range of opposition groups struggling after Putin's victory in March's presidential vote. Opposition members have increasingly tried to focus on local elections and saw the Astrakhan vote as a flagrant example of fraud.

Alexei Navalny, a key organizer of massive street protests in Moscow, visited Astrakhan on Tuesday to meet with Shein and promise support.

``You have found yourself on the forefront of political struggle, defending your dignity and fighting for civil rights,'' Navalny said in a video posted on Shein's blog. ``The entire country is looking at you.''

Navalny and other activists urged supporters to go to Astrakhan for a protest this weekend.

Authorities so far have stonewalled Shein. Local prosecutors said earlier this week their probe had confirmed violations at some polling stations, but insisted they were not widespread and could not have influenced the outcome.

The Central Election Commission said Wednesday that despite some violations the election was fair and its results would stand.

Asked about the Astrakhan vote, Putin responded that it wasn't his job to judge the election's validity and advised Shein to go to court. Russia's judicial system, however, has been weakened by corruption and courts routinely favor the government in their rulings.

``It's a bit weird to go on hunger strike before a court makes its ruling,'' Putin said, prompting Just Russia deputies to storm out. Just Russia has 64 members in the Duma, but it was not clear if all were there Wednesday.

Just Russia leader Sergei Mironov later returned to deliver a speech in which he told Putin that his party has little faith in Astrakhan's courts.

Mironov told Putin his party doesn't understand why he had found no time to look into the alleged fraud.