The press secretary of jailed opposition politician and anticorruption campaigner Aleksei Navalny and the host of Navalny's YouTube channel have been detained in Moscow, according to independent media reports.
Kira Yarmysh and Ruslan Shaveddinov were detained separately by police in Moscow on May 22 and were taken to the Tverskoye police station.
Shaveddinov was detained outside of his Moscow home, he wrote on Twitter.
Yarmysh arrived at the police station to represent Shaveddinov's interests, but was also detained, she tweeted.
According to a lawyer for Navalny's Anticorruption Foundation, Ivan Zhdanov, the two are accused of being among the organizers of a May 5 rally against President Vladimir Putin's reelection.
Under the slogan "He's not our tsar," Navalny, 41, had called on his supporters to take to the streets nationwide ahead of Putin's May 7 inauguration.
According to the independent police-monitoring group OVD-Info, some 1,612 people, including Navalny himself, were detained in 26 cities in connection with the rally, some 7,000 of them just in Moscow.
Navalny was initially released, but a Moscow court on May 15 ordered him to be jailed for 30 days after finding him guilty of repeatedly violating regulations for organizing public gatherings.
Shaveddinov's detention is the second in less than a week, after police in Moscow arrested him for a short period of time over the same accusation of involvement in the May 5 protests.
In January, both Yarmysh and Shaveddinov were sentenced to several days in jail for broadcasting Navalny-organized rallies calling for a boycott of the March 18 presidential election.
Putin, 65, has president or prime minister since 1999. He was reelected by a landslide on March 18, in a vote that has called a demonstration of public trust but critics say was marred by fraud and what international observers said was the lack of a genuine choice.