African migrants who thought they would be denied passage to Europe became violent and threatened to kill the crew of an Italian supply ship that had rescued them.

Vos Thalassa, a specialist Offshore Supply Ship which works supporting French oil and gas company Total, picked up more than 60 migrants after responding to a distress call in the Mediterranean on Sunday night.

But within minutes, the crew were taken “hostage” by the people they allowed onboard, according to Il Giornale, which reported that some of the individuals who were rescued became enraged when a Libyan coastguard boat arrived on the scene to take the illegal immigrants to safety.

“It turned from a rescue to piracy,” commented the Italian transport ministry, stating that “death threats were made”.

Libyan Coast Guard spokesman Admiral Ayoub Qassem said: “The tugboat, which had been hired by Libya for logistics operations supporting some oil platforms off our coasts, intervened to rescue 63 people aboard a wooden boat.”

The migrants grew increasingly aggressive and threatened to kill the crew “because they did not want to return to Libya in any way” when they saw the boat, “forcing it to head north”, he added.

“We did not want to do anything that could further degenerate the situation. Our priority was to ensure the safety of the crew and all the other people,” Qassem told Italian Journalist Agency (AGI), adding he feared the incident could be the first of many “migrant revolts” to come.

On Monday the migrants were passed over to an Italian coastguard boat, which intervened after being alerted to a “situation of serious danger for the security of the [Vos Thalassa] and its crew … caused by attitudes threatening the crew by some migrants”, according to a statement.

Italian Transport Minister Danilo Toninelli said he was “proud” of the country’s Coast Guard for taking the migrants “who were endangering the life of the Italian cruiser Vos Thalassa”, writing on Twitter: “Now onwards with investigations to punish troublemakers.”

However, government sources said the private tugboat’s intervention was “not necessary” because the rescue was the responsibility of the Libyan Coast Guard, which was close by.

Italy’s Interior Minister Matteo Salvini on Tuesday posted a transport ministry list of the migrants’ nationalities revealing that the bulk of hail from safe countries, commenting that few of the newcomers appear to have escaped conflict zones.

The patriotic League minister announced at the end of last month that the nation’s ports would be closed “all summer” to foreign NGO boats which have ferried hundreds of thousands of mainly sub-Saharan migrants to the southern European nation in recent years.