Helsinki's concerns follow the sinking of the Prestige tanker off Spain in November, which left beaches coated in fuel oil, destroyed wildlife and put fishermen out of work.

President Tarja Halonen and Prime Minister Paavo Lipponen have appealed to Russia to stop the Suezmax 147,000 deadweight tonnage vessel Stemnitsa being allowed to load some 100,000 tonnes of crude oil at Primorsk. The vessel is due to leave port later yesterday.

"The ice situation is very dangerous at the moment. Since the winter has been so harsh the ice is thicker than normal," said the prime minister's spokesman Mikko Norros.

Finland cannot stop the tanker because it is in international waters, despite sailing close to Helsinki.

Lipponen has asked European Commission President Romano Prodi to raise the issue with Moscow.

Finland is concerned by a rise in the number of crude oil transports through the Gulf of Finland since the construction of the port of Primorsk near the Finnish border in 2001.

"If the vessel is not ice-classed there is a tremendous danger that it will get stuck in the ice and the ice pressure then punctures a hole in the vessel and causes oil leakage," said Markku Mylly at the Finnish Maritime Administration.