Opposition leaders from Moscow arrived in the city of Astrakhan on Tuesday to lend support to mayoral candidate Oleg Shein and his supporters, who are in the fourth week of a hunger strike against purported vote fraud.

Anti-corruption blogger Alexei Navalny joined dozens of local opposition activists in attempting to hold a march to the local elections commission building, Gazeta.ru reported. Police blocked their path, and the activists walked to a central square in the city, where they pitched three tents.

Signs attached to the tents included the opposition slogan "For Fair Elections" and the message "We voted for Shein," according to a photograph posted by Navalny on his Twitter account.

Police increased security in the southern city Tuesday in response to the opposition events, RIA-Novosti reported. Navalny wrote on Twitter that local protesters were surprised to spot a police helicopter flying overhead.

"A police helicopter is flying over Astrakhan. This is new here. Residents are mildly awed," Navalny wrote.

Astrakhan has become a new rallying cry for the country's burgeoning protest movement as key opposition figures have called for support of Shein's 26-day hunger strike.

The mayoral candidate was pale and looked "very morbid" on Tuesday, a Gazeta.ru correspondent said. He has lost nine kilograms and his supporters have become concerned that his health is in danger.