Italian parliamentarians have urged the government to rescue people at sea amid fears that many migrants may have drowned over the weekend as they tried to make their way to Europe from Libya.

EU member states have been accused of abandoning people at sea after failing to respond to information provided by NGOs that four boats, carrying 258 migrants between them, were in distress.

Alarm Phone, a hotline service for migrants in distress at sea, lost contact with three of the boats between Friday and Sunday afternoon. About 47 people on the fourth boat were rescued on Monday morning by SMH, a Spanish NGO. In calls made to Alarm Phone from the boat, which was at sea in freezing temperatures for four nights, migrants said five people were unconscious and that a pregnant woman and her seven-year-old child were in need of urgent medical help.

“They were really in a dire state,” said Maurice Stierl, a researcher at the University of Warwick and member of Alarm Phone.

“It’s ridiculous: EU states have known about this for 58 hours and have failed to intervene. We have no idea where the other three boats are, whether the people might have been rescued or whether they drowned.

“Some sources say there may have been one shipwreck but it’s difficult to match boats that have capsized as there is no evidence and they simply disappear. There is also no evidence because states refrain from sharing information, and so we have asked Italy, Malta, Libya and the EU to provide information.”

The boats are said to have been in distress in waters between Malta and Italy. On Saturday, the Maltese government banned rescue ships from bringing migrants to Malta.

The decision came a few days after the Italian government declared its own ports “unsafe” as the country struggles to contain the coronavirus pandemic. Libya, where thousands of migrants are kept in detention camps, also closed its ports in March.

But migrants are still attempting journeys from Libya. On Sunday, Italy’s transport ministry ordered those onboard the Alan Kurdi, a ship run by the German NGO Sea-Eye, to be moved to another vessel and tested and quarantined rather than be permitted to disembark.

In a letter addressed to the prime minister, Giuseppe Conte, on Sunday, the 23 Italian MPs and three MEPs, wrote: “We implore you to act quickly to help those who need to be rescued at sea. We hear news of a shipwreck, of boats laden with humanity, desperately trying to reach the European coast. We ask the Italian government to intervene before it is too late.”

Gregorio De Falco, one of the senators who signed the letter, said: “This is the time of year when migrant arrivals increase as the sea is usually calmer. In addition, there have been bombings in Libya very close to the coast where migrants are kept in detention centres … and so this pushes them to try and leave.”

In Italy’s unprecedented decree last week, the government said it would block the arrival of migrant rescue ships until the end of the coronavirus emergency. The decree was signed by the interior minister, Luciana Lamorgese; the health minister, Roberto Speranza; the foreign minister, Luigi Di Maio; and the infrastructure minister, Paola De Micheli.

“This decree is really ignominious,” De Falco added. “Coronavirus is being used as an excuse to say that Italy, and its people, would not be safe for shipwrecks or for migrants in general.”

The EU has been criticised for failing to act. The Italian unit of Sea-Watch, the German NGO, tweeted on Sunday: “Left to die alone on the day of Easter by a Europe that speaks emptily of solidarity towards people who suffer.”