Wojtek Radwanski/AFP via Getty Images

Rallies were held in dozens of cities across Russia on Wednesday in support of jailed opposition leader Alexei Navalny, who is now in his third week of a hunger strike.

OVD-Info, a monitoring group, said 1,496 protesters were arrested, including 662 in St. Petersburg. The rallies coincided with Russian President Vladimir Putin's annual address to the country, and while he did not mention Navalny, Putin did warn "whomever organizes any provocations that threaten our core security will regret this like they've never regretted anything before."

Navalny, who survived a nerve agent attack last year, was arrested in January after returning to Russia from Germany. The 44-year-old began his hunger strike over what he said was the prison's failure to properly treat him for back and leg pain. Navalny's allies say he is in declining health and at risk of cardiac arrest and kidney failure, and they want him to be able to see his own doctors. Russia's human rights commissioner on Tuesday said four doctors have visited Navalny, and he has no serious health problems.

Navalny's wife, Yulia, attended the Moscow rally, where supporters chanted, "Freedom to Navalny!" and "Let the doctors in!" Before the rally began, Navalny's spokeswoman, Kira Yarmysh, and ally Lyubov Sobol were detained at their homes, and Yarmysh has been jailed for 10 days after being accused of inciting protesters. "This is repression," Navalny aide Ruslan Shaveddinov tweeted. "This cannot be accepted. We need to fight this darkness."