Russian Prime Minister Dmitry Medvedev says authorities will shut down a paper mill on the shores of Lake Baikal, which environmentalists say is a major pollutant threatening the world's largest fresh water lake.

Authorities first closed the Baikal Pulp and Paper Mill in 2008 before it re-opened in 2010. Then Prime Minister Vladimir Putin stressed then that the employment of the mill's 1,500 workers in the eastern Siberia town of Baikalsk superseded ecological concerns.

Environmentalists said that the mill threatens the lake's estimated 1,500 unique species of plants and animals.

Medvedev, who was visiting Lake Baikal on Tuesday, said "there's no way back" on the latest decision to close the plant, Russian news agencies reported.

The prime minister also pledged nearly $1 billion toward the development of the area.