Four protected shearwaters died on the coast of Comino on Sunday morning after they were caught on a fishing line.

A video posted on the Facebook 'closed' group Rubs Puppy Love, shows two men on a boat trying to rescue the struggling birds. 

Ten birds can be seen in all, some of them floating and not moving.

The video poster said all birds were freed except for the four that were already dead. 

A spokesperson from BirdLife said that 18 birds were freed and another boat had found one more bird injured. This will be taken to a vet. 

The birds, the spokesman said, were freed by hunters.

"The birds were caught on a long line which was floating, which is not usual," he said. 

"Either the fishermen made a mistake or the long line was cut and floated to the surface, so this was an accident."

The spokesperson said that that such bycatch accidents are not common in Malta, unlike in other European countries. 

Such accidents usually happen in overcast weather, which Malta has experienced in the past few days, he said.

"The shearwater would have tried to eat the bait on the hook and then end up getting caught."

A member of Nature Trust confirmed that some of the birds were released but said four had died. 

The police were also on site.