A boat carrying about 400 people “in distress” has been spotted adrift between Greece and Malta and is taking on water, support services have said.
German NGO Sea-Water International tweeted that those on board were in “imminent danger of death” and called on the EU to act.
Alarm Phone also tweeted its concerns, saying it had received a call from the boat, which departed from Tobruk in Libya.
People on board are panicking and several need medical attention, Alarm Phone said, including a child, a pregnant woman and someone with a physical disability
The vessel is said to be out of fuel and its lower deck is full of water.
The captain has left and there is “nobody who can steer the boat”, Alarm Phone said.
It added that it had alerted the authorities.
The boat is now in the Maltese Search and Rescue area, Alarm Phone added.
There has been a rise in the number of migrant boats crossing the Mediterranean from North Africa recently, Reuters reported.
Another NGO, Germany’s Resqship, said on Sunday that at least 23 migrants died overnight in the Mediterranean in a separate shipwreck.
It tweeted that it found 25 people in the water during a rescue operation.
Last week, 440 migrants were rescued off Malta after a complex 11-hour operation in stormy seas by the Geo Barents
vessel of the Doctors Without Borders (MSF) charity.