Vladimir Putin went fishing at Russia's Lake Baikal in Siberia and warned that the world's deepest freshwater lake, has extremely high pollution levels.
Lake Baikal is a UNESCO World Heritage site, the world's deepest lake at 1,700 metres (5,580 feet) and also the oldest at 25 million years. Tourists flock there to enjoy the unique wildlife and clear waters.
Mr Putin, while meeting officials in a room looking onto the shimmering waters of the lake, complained that "significant areas around Baikal have suffered extremely high pollution."
Saying that Baikal "belongs to the entire planet," Mr Putin insisted that preserving it for future generations is "undoubtedly a government priority."
The Russian president has declared that environmental issues are a personal passion and has spent time tracking whales and tigers and even flown with migrating cranes. In 2009 he went down to the bottom of Lake Baikal in a mini-submarine.
But he was also instrumental in keeping a polluting factory open beside the lake and has presided over a crackdown on environmental activists and non-governmental organisations, including those specifically trying to protect Baikal.
On Friday, Mr Putin called for officials to pay "special attention" to clean up the aftermath of "irrational and often irresponsible economic activity" around the lake, and to prevent such damage happening again.
A giant Soviet-built paper mill right beside the lake sullied its waters for decades but it was finally closed in 2013. Mr Putin had reopened the plant in 2010 after it initially shut in 2008, citing concerns over employment for local residents.
Mr Putin said the lake's waters were now being polluted by household sewage and chemicals from farming, citing the need to "drastically cut down the volume of untreated water being discharged into the lake."
He called for the Prosecutor-General's Office to carry out a check into illegal and environmentally damaging activity around the lake and "take the necessary measures."
In 2013, a group campaigning to protect the lake called Baikal Wave, was dubbed a "foreign agent" under tough new legislation targeting NGOs with foreign funding.
The group, founded in 1990, closed down in 2016, saying it had become impossible for it to function.
