Two Canadian activists are among a group of 25 people who were being held at gunpoint aboard a Greenpeace ship, the environmental group said Thursday.

Arctic Campaign Co-ordinator Christy Ferguson said Paul Ruzycki of Port Colborne, Ont., and a man from Montreal whose name was not released were arrested when Russian coast guard officers boarded their vessel, which Greenpeace says was in international waters.

Ferguson said at least 15 members of the coast guard used helicopters and ropes to rappel on board the Arctic Sunrise, a Greenpeace ship carrying a crew bent on protesting offshore oil drilling in the Arctic.

The crew were being held in the ship's mess, she said, adding no injuries have been reported.

'This was a peaceful protest against reckless industrial activity.'- Christy Ferguson, Greenpeace's arctic campaign co-ordinator 

The incident took place Thursday as the ship was circling an oil platform in the Pechora Sea, an arm of the Barents Sea. The platform was owned by Gazprom, a Russian oil company.

Russia's Interfax news agency reported that the vessel was to be brought to the northern port of Murmansk following the search.

Interfax also quoted the Russian foreign ministry as saying the crew of the vessel took "provocative" actions and posed a threat to human life and the environment in the Arctic region.

"The note of protest that was given to the Dutch ambassador describes the actions of the crew of the Dutch-flagged vessel as provocative and says that they posed a threat to human life and the risk of an environmental catastrophe in the Arctic with unpredictable consequences," it said.

Ferguson decried the incident, saying Russian authorities had no jurisdiction over a ship that was sailing in international waters and no need to resort to threatening tactics.

"This was a peaceful protest against reckless industrial activity in the Arctic," Ferguson said in a telephone interview from Toronto.

"Russian authorities have responded with extreme aggression and force. They've pointed guns at people, they've pointed knives at people. They're arresting people and holding them without information in international waters."

Last month Greenpeace claimed the Russian coast guard had threatened to open fire on the Arctic Sunrise if, as planned, it entered the North Sea Route to protest Arctic oil exploration. 

Tensions high

Ferguson said Ruzycki, who was serving as the chief mate aboard the ship, is a veteran crusader who is no stranger to confrontations.

"He's been sailing with Greenpeace for about 25 years, and he's been in a lot of tense situations and is really committed to this kind of work," she said.

Ruzycki's sister, Patti Ruzycki-Stirling, said news of her brother's detention came as a shock. All was well during their last email correspondence early Thursday morning, she said, adding subsequent events have left the entire family very concerned.

"I got a little sick to my stomach thinking, 'this has taken a turn I don't even want to think about," she said.

Ferguson said tensions have been flaring between the two parties for some time. While on board the ship two weeks ago, Ferguson said she negotiated with Coast Guard officials who were threatening to fire on the Arctic Sunrise if they persisted in their protests.

Earlier this week, Russian officials detained two crew members who were attempting to climb onto an oil platform. Those crew members were held on a Russian ship before being returned to the Arctic Sunrise, she said.

With files from Associated Press and CBC News