MOSCOW: Police detained dozens of demonstrators in Moscow on Saturday as Russian opposition supporters took to the streets in defiance of a formidable security presence, in fresh protests calling for fair elections in the capital next month.

The unauthorised march, which comes after stark warnings from Russian authorities and a crackdown on Kremlin critics, was billed as a "stroll" along Moscow's leafy boulevards as anger grows over the refusal of officials to let popular opposition candidates run in next month's city parliament elections.

Most of those candidates and opposition leaders are still in police detention following the last rally, as what began as a local issue has boiled over into one of the worst political conflicts of recent years.

At least 89 were detained by police about an hour into the rally, according to OVD-Info, a non-governmental organisation that operates a hotline for detainees. AFP correspondents also observed several arrests.

Lyubov Sobol, an ally of key opposition leader Alexei Navalny, was detained as she set off for the rally. "Why are you detaining me?" she shouted as riot police in helmets dragged her out of a taxi.

Sobol is on the 21st day of a hunger strike that she began after authorities barred her from running in the polls and was visibly weak.

Heavy police presence, metal barriers and empty buses used to transport detainees lined the boulevards, and mobile internet was down in central Moscow. Some shops and cafes were shut Saturday following warnings by city authorities.

Amount of police appeared to outnumber small groups of protesters. About a hundred people were pushed out from central Trubnaya square by a line of riot police. Several hundred more were spread out along the boulevards.

"I'm here because I want them to let candidates take part in the elections," 22-year-old artist Varvara told AFP. "I want there to be big changes... now there is an atmosphere of total control."

At least six people were detained about 30 minutes after the planned start of the rally, according to OVD-Info website.

- Navalny 'poisoned' -

Candidates for September elections needed to collect signatures from city residents to stand in the polls but officials said they were disqualified because some names were forged.

The opposition insists it was blocked from running arbitrarily, and the whole vetting process was skewed against them.

Many Muscovites said their signatures in support of opposition candidates were declared invalid for no reason, and attempts to verify them were ignored.

President Vladimir Putin has yet to comment on the situation in Moscow.

In the polls in September, the opposition hopes to end the monopoly of Kremlin loyalists in Moscow's parliament.

The body decides the city's multi-billion-dollar budget but lacks political independence from mayor Sergei Sobyanin, an ally of Putin.

Sobyanin has warned the opposition against "new provocations".

Navalny and other protest leaders argue corruption is rife in the capital.

Navalny, currently in jail, was rushed to hospital last weekend in an incident his personal doctor blamed on possible poisoning with an unknown chemical substance.

A state toxicology lab said no traces were found. —AFP