(AP) MOSCOW – Russian authorities should annul the results of the parliamentary vote and hold a new one, former Soviet leader Mikhail Gorbachev urged Wednesday as popular indignation grew over widespread allegations of election fraud.

The call for an entirely new vote by the last president of the Soviet Union was a remarkable development for an election that had not generated much interest during the campaign. Prime Minister Vladimir Putin had wanted to see his United Russia party do well to pave the way for his return to the presidency, but few Russians seemed to care about the vote, with many saying they assumed the results would be manipulated anyway.

United Russia won less than 50 percent of Sunday’s vote, a steep fall from the 64 percent it won four years ago. But opposition parties and independent observers say even that result was inflated by vote-rigging, including alleged ballot-box stuffing and false voter rolls.

Gorbachev told the Interfax news agency that authorities must hold a fresh election or deal with a rising tide of discontent.

“More and more people are starting to believe that the election results are not fair,” he told Interfax. “I believe that ignoring public opinion discredits the authorities and destabilizes the situation.”

Surprisingly, thousands of Russians have rallied in Moscow and St. Petersburg in the last two days, facing off against tens of thousands of police and Interior Ministry troops. Hundreds of protesters have been detained in both cities. The unusually sustained protests suggests Putin’s drive to regain his old job may not go as smoothly as he had expected.

The malaise revealed in Sunday’s parliamentary election suggested Russians are tiring of Putin and his United Russia party, which has dominated all other political forces in Russia for the past dozen years and earned a reputation for corruption.

Gorbachev added that authorities “must admit that there have been numerous falsifications and ballot box stuffing.”

He spoke on the same day that Putin officially registered to run for the presidency in a March vote.

Putin served as president from 2000 to 2008, when he moved into the prime minister’s office because of a constitutional limit of two consecutive presidential terms. A constitutional amendment pushed through parliament by United Russia extended the presidential term from four to six years. Under it, Putin, 59, could theoretically serve as Russia’s leader until 2024.

The 80-year-old Gorbachev, leader of the Soviet Union from 1985 until its breakup in 1991, has long had tense relations with Putin, but until recent years had refrained from directing his criticism of Russian politics at Putin.

Putin has been extremely critical of Gorbachev’s legacy, including his concession to what many Russians saw as Western pressure to pull Soviet troops out of Germany, and has blamed him for the Soviet Union’s demise.

Thousands of security forces were out in the Russian capital and helicopters roamed the sky Wednesday, a show of force following two days of protest. More opposition rallies were expected later in the day.

The Interior Ministry said Tuesday at least 51,500 police officers and 2,000 paramilitary troops have been deployed in Moscow since the election.

About 1,000 people gathered at a pro-Putin concert Wednesday afternoon in central Moscow. The crowd of mainly young people waved Russian flags and danced as organizers spoke on a stage adorned with a banner reading “The Future is Ours.”

Someone dressed as a giant white bear — United Russia’s mascot — danced among the crowd. He stopped occasionally to hug supporters — but kept right on dancing when someone ran out of the crowd to kick him in the rear.

College student Ivan Samburov, 17, said he had no interest in the protest rallies.

“I prefer just to stand like this and dance, to have fun and improve my mood, to feel that everything is good,” he said.

The Russian Union of Journalists condemned police violence against protesters and called for an investigation into the dozens of attacks and arrests of journalists, describing them as “an attempt to gag and intimidate society.”

On Wednesday, two video journalists working for the state-owned RIA Novosti news agency were briefly detained outside the Central Election Commission building where Putin was handing in his application to run.

The allegations of election fraud have fired up the opposition, which has long seen its protests crushed and its pleas ignored by the Kremlin-dominated media.

On Facebook, almost 15,000 people signed up to a page announcing an opposition rally for Saturday — and many of them have never taken part in political demonstrations

Mariya Boyarintseva, a 24-year-old event manager, said she has never been to a political rally before but she was going to Saturday’s protest.

Boyarintseva said she didn’t go to the rallies on Monday or Tuesday — which ended with clashes with police and hundreds detained — because “it felt a bit scary.”

“Now, I have a feeling that I ought to go,” she said.