The Italian navy took back control of a Sicilian fishing boat that had been seized overnight by unknown assailants near the Libyan coast, the defence ministry said.
The stretch of Mediterranean Sea has grown increasingly chaotic in recent years as hundreds of thousands of people risk the dangerous journey to Europe to escape conflicts in Libya, other parts of North Africa and the Middle East.
A defence ministry statement said naval personnel boarded the trawler soon after it was stopped by a tugboat around 90 km from the Libyan port of Misrata.
The ministry did not immediately say whether there was any clash with those who had seized the Italian trawler or what happened to them or the seven crew on the vessel after the navy reasserted control.
The statement said the tugboat was probably owned by Libyan security forces, which have stopped such boats in the past due to disputes over fishing territories.
A spokesman for a Sicilian fishing trade association had said earlier that the incident was likely to be the work of pirates. No such attacks have been reported before.
"This is probably an act of piracy because the tugboat that approached the trawler had no Libyan governmental insignia," the spokesman, Francesco Mezzapelle, told Reuters. He said the trawler was manned by three Italians and four Tunisians.
Armed chaos in Libya has been exploited by migrant traffickers who charge thousands of dollars to mainly sub-Saharan Africans for a passage across the Mediterranean to a better life in Europe.
Around 13,000 people have been rescued at sea over the last week as good weather improved sailing conditions. About 1,000 people are reported to have drowned this year and survivors have spoken of harrowing conditions.
Today, an Italian vessel picked up and brought 60-70 migrants to the small island of Lampedusa south of Sicily, the UN refugee agency (UNHCR) said.
Many of the migrants were suffering heavy burns after a gas cylinder explosion that occurred before they had begun their voyage, killing several people and injuring others, she said.
Survivors of the blast, which took place in an area where traffickers hold migrants before loading them onto boats, included children, and one 25-year-old woman died onboard.
"The traffickers would not allow them to leave and reach the hospital so they didn't get treatment for a few days and then they were put on a boat," UNHCR spokeswoman Barbara Molinario said on Lampedusa.
Police in Ragusa, Sicily, said they had arrested a Tunisian people trafficker as he arrived with a boatload of migrants.
Yesterday, 15 African Muslims were arrested on suspicion of murder after survivors from a packed migrant boat accused them of having thrown 12 Christians into the sea in a row that broke out after people on board began praying for their lives.