Moscow, Sep 20 (IANS) A ship with 28 environmental activists of global voluntary organisation Greenpeace on board was seized by the Russian military allegedly in international waters early Friday, Sky News Australia reported.

The Arctic Sunrise was seized by Russia's federal security service FSB, which controls the border guards. It has accused the vessel's captain of carrying out "unlawful activities".

Russian border authorities said the vessel would be towed to Murmansk port, some 1,500 km north of the Russian capital Moscow.

"The Arctic Sunrise will be taken to the port of Murmansk for further legal procedures," a spokesperson for FSB said.

However, Greenpeace said that the ship was sailing peacefully when security forces dropped by rope from helicopters and arrested its crew at gunpoint. 

Roman Dolgov, a detained activist, said that he and his colleagues have been accused of "terrorism".

"We are facing quite serious accusations: of terrorism and carrying out illegal scientific research," he said from the ship.

Greenpeace Australia chief executive David Ritter said that two Australians were among the 28 activists detained on the Sunrise and one of them managed to radio back an SOS just after the ship was overrun.

The ship was three nautical miles inside international waters when boarded, Ritter claimed.

Russia has accused Greenpeace of "aggressive and provocative" behaviour, saying the activists attempted to "infiltrate" the Prirazlomnaya oil platform owned by Russian energy giant Gazprom, in the Barents sea.

Greenpeace acknowledged two activists did try to get aboard the rig Wednesday but denied their behaviour was aggressive.