Conservationists who attacked a Maltese-owned tuna pen on the high seas may have committed an act of piracy when they rammed the cage with their ship and divers ripped the net to release the fish.

"The actions undertaken by the Sea Shepherds can be described as an act of piracy under the UN Convention on the Law of the Sea, especially if their actions happened in international waters," Captain Reuben Lanfranco, a marine consultant, told The Times.

The tuna pen belonged to Maltese company Fish and Fish and it was being towed by a tug boat and a supply vessel at the time of the attack. Two divers had to be airlifted to hospital after sustaining injuries in the skirmish with Sea Shepherd members.

The law of the sea defines piracy as "any illegal acts of violence or detention, or any act of depredation, committed for private ends by the crew or the passengers of a private ship or a private aircraft".

"A boat hook is also a form of weapon and tearing the net and releasing tuna could be tantamount to destruction and damage," Capt. Lanfranco said, insisting that if the conservation group suspected any illegality it still had no right to take the law into its own hands.

In his first reaction to the incident, Rural Affairs Minister George Pullicino had defended the fishing operation, insisting it was legal and within the EU's parameters.

A spokesman for his ministry, which is also responsible for fisheries, said all documentation confirming the tuna was caught legally was on board the tug boats as per EU regulations and International Commission for the Conservation of Atlantic Tuna (ICCAT) recommendations.

"No tuna is caged in Malta unless the flag state of the ship making the catch gives authorisation and issues a validated blue fin tuna catch document registered with ICCAT. All catching, transfer and harvesting operations are subject to verification under the regional observer programme," the spokesman said.

Thursday's incident was the second in the span of a week after a Greenpeace ship on Sunday tried to release tuna from a cage belonging to another Maltese company. Their actions were thwarted by fishermen and a patrol boat of the Armed Forces of Malta.

The drama on the high seas terrified tugboat workers, according to Kevin Attard, a director of a shipping company that charters towing vessels for tuna operators. His vessels were involved in Sunday's incident with Greenpeace.

"These are not fishing boats but tugboats that are towing the cages to their final destination. It is not fair on my employees to be victimised by Greenpeace or anybody else when they are going about their job in a perfectly legal way," Mr Attard said.

His company has four boats out at sea and family members of crews on board the vessels are anxious about what could happen to their relatives.

"Tuna fishing is legal and it is very closely monitored by ICCAT observers. It is an important industry for Malta because the economic spin-off leaves a lot of cash here and generates jobs. We are doing our job legally," Mr Attard insisted.

Condemnation of the conservationists' actions continued to pour in yesterday with the Labour Party insisting the government take legal action against Sea Shepherd and ensure protection for workers at sea.

Commenting on the incidents, Nationalist MEP Simon Busuttil said environmental organisations that damaged private property to reach their aims were putting themselves in a state of illegality. He said this was a matter of great concern and appealed for moderation and respect to the rule of law.

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