A migrant aboard a rubber dinghy off the Libyan coast is helped by rescuers aboard the Open Arms aid boat, of Proactiva Open Arms Spanish NGO. File picture: Olmo Calvo/AP

Rome - A migrant boat on the sea stretch between Libya and southern Europe is in distress with 150 people on board, activists said on Monday.

Alarm Phone, an organization that takes calls from migrant boats in distress, wrote on Twitter it was contacted by a vessel that took off from Khoms, east of the Libyan capital Tripoli.

"They say 50-60 women & 30 children among them! There are sick & pregnant ppl. Their engine stopped working. No rescue in sight - authorities in #Italy and #Malta were informed around noon," it said.

Alarm Phone later said it lost contact with the boat and that Italian authorities had turned over responsibility for the rescue to their Libyan counterparts.

"Very concerned about this situation. No one is aware of ANY ongoing rescue operations at the moment," Flavio Di Giacomo, a spokesman for the International Organization for Migration (IOM), tweeted.

"These people are in grave danger and risking their lives and they must be saved," Di Giacomo added.

Human rights groups have repeatedly criticized Italy and the European Union for allowing migrants intercepted at sea to be sent back to Libya.

In January, Human Rights Watch released a 70-page report called "No Escape from Hell: EU Policies Contribute to Abuse of Migrants in Libya."

It claimed that migrants in overcrowded Libyan detention camps, including children, have no access to decent food, healthcare or sanitation, and are routinely beaten up by guards.