About 500 tonnes of oil leaked into the River Dulov from a factory involved in developing space rocket technology, according to the organisation.

But campaigners said officials had played down the size of the spill, which is believed to have killed about 100 ducks.

There were also fears that the oil could seep into drinking water.

WWF said ice was the only thing preventing the oil from seeping into the River Klyazma, the main water source for thousands of people living to the east of Moscow.

Officials from Moscow’s emergency department told local media the event was not an environmental disaster.

Volunteers from WWF Russia spent New Year rescuing birds in the Black Sea Strait affected by a November oil spill.

About 2,000 metric tons of fuel spilt into the sea on November 11 after a storm in the Kerch Strait sank four ships and an oil tanker.

Following the accident, WWF and other environmental NGOs called on the Russian government to train volunteers to respond to oil spills, develop legislation governing oil spills and set up an independent agency responsible for environmental protection.

Kate Martin

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