Protesters in Moscow say this month's parliamentary elections were rigged, and they expressed growing discontent with Vladimir Putin's era of control in Russia, roughly four months before Putin will once again be a candidate for president.

The crowd of 50,000 that flocked to an island near the Kremlin was the largest protest group since the fall of the Soviet Union, the BBC reports. The New York Times focuses on just how much the protesters are turning on Putin, who they suspect of helping to rig parliamentary contests in favor of his chosen candidates: main chants at the rally included "Putin is a Thief" and "Russia Without Putin."

More from The Wall Street Journal:

In the Dec. 4 vote, the ruling United Russia party of Prime Minister Vladimir Putin saw its support drop sharply, but still retained a majority in parliament. But local and foreign observers reported widespread stuffing of ballot boxes and other abuses, many of which have been spread by reports and recordings on the Internet. U.S. and other Western governments have raised questions about what they say are suspicions of widespread fraud.

"I haven't walked in a demonstration like this in a long time," said Gennady Gudkov, a member of parliament from the Just Russia party, as he walked with thousands of others to the main rally. "The people have really awoken. The authorities can't ignore this many people."

In Moscow and St. Petersburg, the country's largest cities, protests built over the days since the vote, drawing many demonstrators who hadn't attended such actions in the past.

So far, no violence, the BBC reported, quoting a prominent opposition figure, Yevgenia Chirikova. "Our action is peaceful, we hold the most civilized protest on planet," she said.

Would this discontent with a leader hasten the sort of abrupt turn and downfall that marked the Arab Spring of 2011? There was no telling, but one indicator showed longterm concern. That would be the markets. It's still unlikely that Putin and his allies would lose their firm grip on the country, but investors are spooked by the protests — and the undemocratic nature of government that protesters say has typified Putin's reign.

Foreign investors are worried about Russia, Reuters notes.

Eoghan Flanagan, head of emerging markets equities at fund manager Liontrust in London had already cut exposure to Russia before the election, mainly as part of a euro zone crisis risl reduction.

But he is now concerned about the risk of turmoil like that which toppled long-time Egyptian leader Hosni Mubarak but sent the country's economy into a tailspin and led to massive investment outflows.

The election turmoil has pushed Russian stocks down 8.5 percent this week, with Tuesday seeing a 5 percent selloff.

"Everyone who invests in Russia knows they are investing in a status quo that doesn't have very deep roots in democracy," Flanaghan said, adding the possibility of an Egypt-type scenario in Russia had gone "from zero to 5 percent."