Greenpeace activists tried to break open a tuna pen belonging to a local company as it was being towed back to Malta with its catch yesterday afternoon.

The Armed Forces of Malta said a Greenpeace ship, the Arctic Sunrise, tried to sail into the pen and activists on dinghies attempted to tear it open. A second Greenpeace vessel, the Rainbow Warrior, was also present.

The outnumbered fishermen towing the pen radioed for assistance and a patrol boat out at sea and a military helicopter were sent to the scene, the AFM said.

With the activists adamant on freeing the tuna, the patrol boat was forced to block the ships' path and use its fire hoses to repel the protesters in what turned out to be a two-hour-long skirmish 22 nautical miles to the south of the island.

No one was injured in the incident and it is understood that no tuna escaped. But the environmental organisation, describing its actions as "non-violent", claimed that flares were shot at the activists by the fishermen.

The Times' attempts to contact the fishermen out at sea failed due to communication difficulties. The company involved is Ta' Mattew Fish Farms Ltd.

Greenpeace is currently on a crusade against the capture of bluefin tuna to be fattened in captivity and sold later. It has been patrolling the Mediterranean in a bid to thwart the fishermen.

Commenting about its actions yesterday, it said it only wanted to free the fish, which was a highly endangered species.

Oliver Knowles, the organisation's oceans campaigner, said releasing tuna was the only responsible thing to do to safeguard the future of the species and the ocean.

He insisted that activists would confront any and all parts of the industry, which was a clear example of how politics had failed the seas. However, the Ministry for Resources and Rural Affairs said in a statement that the tuna in the pen had been legally caught and made up part of the internationally established quota.

It maintained that local fishery activities were being carried out in accordance with regulations laid down by the International Commission for the Conservation of Atlantic Tunas and the European Union, who constantly monitored these activities.

There was another clash between Greenpeace and foreign fishermen a couple of days ago, when a grappling hook was hurled at a dinghy and pierced the leg of an activist.