MOSCOW: A leak from Russia's new Siberian oil pipeline shows the potentially damaging consequences the project could have for the endangered Siberian tiger, an environmental campaign group warned on Friday.

Around 300 cubic metres (10,600 cubic feet) of oil leaked from the pipeline in eastern Siberia, Igor Dyomin, spokesman for Russian oil pipeline monopoly Transneft told AFP.

The leak covered an area 10 metres (yards) across and two kilometres (1.2 miles) long, he said.

"The major accident on the new Siberia-Pacific oil pipeline which has just come into operation shows the project has major flaws around ecological safety," the environmental campaign group WWF said in a statement.

"The WWF is worried about the planned extension of the pipeline through the Siberian tiger's habitat."

The first section of the pipeline, linking Taishet in eastern Siberia with Skovorodino in the Amur region, entered service in December.

A second section is planned which will run 2,100 kilometres (1,300 miles) from Skovorodino to the Kozmino oil terminal near the Pacific Ocean port of Nakhodka.

Russia, the world's largest exporter of crude oil, hopes the route will help it diversify its customer base away from Europe by supplying energy-hungry Asian nations.

"A discharge of oil took place during regulatory work on the pipeline," Dyomin said.

"We are trying to establish the cause, but it is not connected to the operation of the pipeline. We have not ruled out human error," he said, adding that the results of the investigation were expected in a month.

The WWF said the causes of the accident should be assessed in public and called for a fresh assessment of the second stage of the pipeline project, involving all parties.

Far eastern Russia is the main habitat for the Siberian tiger, the world's largest feline.

Around 450 remain in the wild there, and a further 20 to 25 live in China.