An Italian fishing boat with seven fishermen on board has been seized by armed men off the Libyan coast while sailing in international waters on the night of 16 April, according to reports.

The fishing boat Airone from Mazara del Vallo, Sicily, was off the Misrata coast when it was hijacked by the gunmen. Seven fishermen - three Italians and four Tunisians - were on board. Another fishing boat nearby at the time of the incident alerted authorities.

"It was a piracy act," Francesco Agusta, spokesman for the COSVAP Sicilian fishermen's consortium, told IBTimes UK. "The boat was taken at 40 miles from the Libyan coast in international water by a military tug boat with no flags or signs from the Libyan government."

He added that the boat's traceability system was switched off by the alleged pirates. "Misrata and Benghazi are in the hands of militia. This is an act of force in international waters," Agusta said.

The crew were fishing for shrimp. It was not clear if shots were fired, and there were no reports of injuries, according to the consortium.

"We are really worried because we don't understand whether it's been seized by the Libyan military or pirates," said Giovanni Tumbiolo, president of the cooperative. "We have alerted the Libyan ministry for Fishery and Agriculture [which said] it was not informed about the incident."

The consortium said there have been a dozen of seizures of Italian fishing vessels since 2005 when Libya asserted that its territorial waters extended more than 70 miles off shore. "This is not recognised by the international community," Agusta said.

The incident occurred after 400 migrants fleeing Libya are feared to have drowned when their boat capsized 24 hours after departing the North African coast. Italy's coastguard rescued 144 people but several hundred others are feared dead given the size of the vessel.

Libya is divided between east and west, with rival parliaments backed by warring militias.

UPDATE: AP reports that the Italian navy has taken control of the boat.