Russian authorities have declared a "high alert" and are distributing masks and respirators to residents of a town outside Moscow where toxic fumes have leaked from a landfill site.

The measures went into effect on March 30 in Volokolamsk, a town of around 20,000 people about 120 kilometers west of Moscow, after thousands of residents on March 29 held a rally demanding that authorities formally declare a state of emergency.

Another rally is planned for April 1, with residents demanding the closure of the landfill, first opened in 2008, that has been emitting a noxious sulphurous smell.

Last week, hospitals treated dozens of children who complained of dizziness and nausea because of fumes from the Yadrovo landfill site near the town.

A spokesman for the regional Emergency Situations Ministry said that "a state of high alert" had been imposed in the town as of March 30 and that monitoring of the environment "will be stepped up" with "nonstop" testing of air quality.

The spokesman said local authorities had also begun distributing medical masks and respirators to those who need them.

The Emergency Situations Ministry said there was no need to evacuate residents or declare a formal state of emergency because air pollution levels as of March 30 did not exceed permissible limits.

Officials have said they will stop adding to the waste dump by the end of the month and install a decontamination system by June, which they said should protect residents until a new facility is eventually built.

Several weeks ago on March 7, Volokolamsk authorities declared a temporary state of emergency, saying the level of hydrogen sulphide in the air was recorded as 2.5 times higher and the level of nitric oxide was double usual levels because of a gas leak at the landfill.

Demonstrations demanding the closure of landfill sites have also been held in several other cities in the Moscow region.

In Kolomna, a historic city of some 140,000 inhabitants about 100 kilometers southeast of Moscow, more than 100 protesters last week attempted to block a road used by trucks taking trash to a landfill site.

Police briefly detained some 30 participants on March 28 and charged three of them with breaches of the peace and disobeying police, said the OVD-Info website that monitors law enforcement activity in Russia.

"We're treated like second-class citizens," a female protester told a local official in a video posted online. "Why are we [treated] worse than Muscovites?"

In the city of Klin, northeast of Moscow, residents have also expressed concern over landfills.

The growing public discontent throughout Russia has forced the authorities to acknowledge problems, including the lack of an adequately funded and equipped service to monitor air quality around the country.

Russia sends almost all its garbage to landfills and there is no obligation for people to recycle household waste, creating a growing problem despite the country's vast territory.

"We are in constant touch with the regional authorities and the government over this," President Vladimir Putin's spokesman Dmitry Peskov told reporters in Moscow on March 30.

"Everyone understands that this is a complicated problem, that it cannot be solved overnight," he said.

With reporting by AFP and Interfax