CAIRO (AP) — A humanitarian group says Libya’s coast guard fired upon its vessel as it searched for a migrant boat in distress in the Mediterranean Sea.

The nonprofit SOS Mediterranee released details of the confrontation Monday. It said the Libyan coast guard shot at the vessel in international waters for 20 minutes on Sunday afternoon, about 40 nautical miles north of the Libyan coast.

No casualties were reported, although the group said the vessel had significant damage.

The attack appeared to be one of the most violent involving a European rescue ship and the Libyan coast guard, which receives training, equipment and funding from the European Union.

A coast guard spokesman didn’t respond to a request for comment.

SOS Mediterranee charters the Norwegian-flagged Ocean Viking in partnership with the International Federation of Red Cross and Red Crescent Societies.

The Ocean Viking was on its way to Italy on Monday with 87 migrants it had rescued from other boats before the attack.

“We demand a full investigation into the events of yesterday afternoon and that those responsible for these life–threatening attacks be brought to justice," said Soazic Dupuy, director of operations at SOS Mediterranee.