'The Environment Ministry estimates that this was a very dangerous ecological accident,' said Alexander Shuval, the ministry's press chief. But Mr Shuval stuck to earlier Russian estimates, that put the amount of oil spilled at 14,000 tons.
A US oil company has said the rupture of a big pipeline sent 272,000 tons of oil flooding into the Pechora basin. That could make it eight times the size of the 1989 Exxon Valdez disaster, which polluted a stretch of Alaskan coastline.
A team of Russian experts has already flown to the site in the Komi republic, over 1,000km (700 miles) north-east of Moscow, but officials have said their report will not be ready for about 10 days.
Mr Shuval admitted that oil had flowed into other rivers in the region late last month when heavy rains destroyed dams built to hold back the oil from an earlier leak. But tests carried out on fish taken from the Pechora this week showed the river itself was not polluted, he said. Land near the point of the pipeline rupture was consistently being monitored, and would remain under observation until a clean-up operation ended by the end of next March, he added.
The pipeline, which carries oil from the Arctic to refineries in central Russia, sprang a series of leaks in August. Western oil experts, charging that 10 per cent of Russian oil leaks away each year, said it was a disaster waiting to happen.
'Many of the (former Soviet) pipelines suffer considerable corrosion,' said Egil Bergsager, of Norway's Rogalandsforskning Institute in Stavanger. 'I would not be surprised if we get more accidents like this.'
The environmental group Greenpeace said Russian firms pumped oil down the damaged pipeline, although it had 'as many holes as a Swiss cheese'. The pipeline company, Transneft, denied the charge.
Mr Shuval said Western media had overreacted to the accident. 'Of course the situation is dangerous,' he said. 'We are talking about a considerable area, but there is no pollution of the (Pechora) river.'Reuse content