A boat with refugees and migrants arrives at Skala Sikaminias, on the Greek island of Lesbos, Greece, Feb. 29, 2020. (Xinhua/Marios Lolos)

Europe's coast guard agency said Sunday it was looking for a dinghy believed to be carrying dozens of migrants when it went missing after setting sail from Libya for Italy.

The UN refugee agency told AFP it was "very worried" about the fate of what could be 85 migrants lost in Mediterranean Sea.

Two German monitors of dangerous migrant crossings first reported spotting four boats in distress off the southern coast of Malta over the weekend.

The European Union's Frontex border guard and coast guard agency later told AFP that one of the four boats had safely reached Italy and another two were still at sea.

It said a fourth boat initially spotted on Friday was unaccounted for.

"Frontex plane will fly again [Monday] morning in search of the remaining boat," a spokesman told AFP.

A spokeswoman for the United Nations High Commissioner for Refugees (UNHCR) said it appeared that the missing boat had capsized.

"We are very worried," UNHCR spokeswoman Carlotta Sami told AFP.

Frontex said it had notified the coast guard authorities of Italy and Malta about the boats at sea.

Neither country's border authorities commented on the reported shipwreck when contacted by AFP.

Germany's Sea-Watch International group showed the boats' geolocation on its official Twitter account.

Sea-Watch presumed that the lost boat was carrying 85 people. It said the other three boats were carrying 173 migrants in all.

Germany's United4Rescue monitor of migrant crossings said in a statement that it was receiving the same reports and feared for the lives of "dozens."

Italy has long established itself as the primary European port of entry for migrants seeking refuge from Africa and the Middle East.

But the Mediterranean country shut down its ports and said it would quarantine any illegal migrants because of the coronavirus pandemic.

AFP