The Finnish Maritime Administration said the vessels are currently stuck off the coast of Finland in the pack ice, which ice breakers are trying to clear.

"They collided again, but it's not serious," said Markku Mylly, responsible for ice breaking at the maritime authority.

The two vessels first collided on Monday with slight damage to the Bremer Saturn.

"There is still a lot of ice and ice pressure because the winds are pushing the ice together, so it's not good, it's difficult for ships in the Baltic Sea," he said.

Both vessels were ice classed and believed to be single hulled, Mylly said.

Finland is concerned about the icy sea conditions this winter, fearing an environmental disaster should an oil tanker not sufficiently protected against the thick ice suffer damanges and cause an oil spill.

Port authorities in Finland, Russia and Estonia are assisting vessels through the ice.