Russian oil spill

Diesel oil from a huge spill in Russia's Arctic north has polluted a large freshwater lake and there is a risk it could spread into the Arctic Ocean, a senior Russian official says.

Emergency teams are trying to contain the oil, which has now travelled about 20km (12 miles) north of Norilsk from a collapsed fuel tank.

It is the worst accident of its kind in modern times in Russia's Arctic region, environmentalists and officials say.

The oil started leaking on 29 May.

So far about 21,000 tonnes have contaminated the Ambarnaya river and surrounding subsoil.

Investigators believe the storage tank near Norilsk sank because of melting permafrost, which weakened its supports. The Arctic has had weeks of unusually warm weather, probably a symptom of global warming.

The power plant where it happened is run by a subsidiary of Norilsk Nickel, the world's leading nickel and palladium producer.

Lake Pyasino serves as the basin for the Pyasina river, which flows to the Kara Sea, part of the Arctic Ocean. From October to June that river is usually ice-bound.

"The fuel has got into Lake Pyasino," said Alexander Uss, governor of Krasnoyarsk region.

"This is a beautiful lake about 70km [45 miles] long. Naturally, it has both fish and a good biosphere," Interfax news agency quoted him as saying.

"Now it's important to prevent it from getting into the Pyasina river, which flows north. That should be possible."