The Propontis ran aground to the west of Hogland island in the Gulf of Finland aroung 2345 GMT, not long after leaving the Russian port of Primorsk.

"The ship is anchored in international waters. There is no problem. Its ... engines are okay, it's able to move by itself," Finnish coast guard commander Marko Tuominen told AFP.

Juha Vuolli, the deputy coast guard commander for the zone, said the shipping company that owns the vessel, Tsakos, had informed him that there were two holes in the hull but that it was a double-hulled vessel.

Divers inspected the hull on Friday afternoon, and were expected to submit their report to a maritime classification group in the evening.

A coast guard helicopter had been sent to the scene and reported seeing no oil, Vuolli said, adding that the tanker must have drifted out of its shipping lane.

The waters were calm and there was no ice in the area, he said.

Finnish oil company Neste Oil, which chartered the ship, meanwhile said there were "some ruptures in the ship's ballast tanks but the cargo space is intact".

The 25-member crew, consisting of Greeks and Filipinos, was unhurt.

Tuominen said the tanker briefly touched the bottom at a shallow point, then drifted 15 nautical miles.

"It very probably deviated from its route for an unknown reason. The big tankers have to follow special (shipping) routes. This one has a draught of 14.4 meters," said Vuolli.

The 250-metre (800-foot) tanker was built in South Korea and delivered in October 2006.

In Athens, Tsakos insisted that there was no risk of an oil spill.

"There is no pollution and no risk that there will be, thanks to the boat's construction since it has a double-hull," spokesman Alan Johnson told AFP.

Tsakos has sent a team of experts to the scene to establish the cause of the accident.

Tankers sailing to and from oil terminals in Russia, Estonia and Finland must pass through the Gulf of Finland, which is about 400 kilometers (250 miles) long and around 100 kilometers (60 miles) wide.

Serious accidents are rare, but environmentalists have expressed concerns about the rapid rise in shipping traffic in the Baltic Sea as Russian oil exports surge.

"This incident raises once again the question of how big the tankers allowed in the Gulf of Finland should be, considering the narrow strait leading to Primorsk," Greenpeace Finland spokesman Mikael Sjoevall said.

"This clearly shows it's just a matter of time before we see a serious accident in the Gulf of Finland."

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