At least four people are dead after a boat carrying migrants on the Mediterranean Sea came under attack off the coast of Libya, a German humanitarian group said.

The Sea Watch organization said Friday’s attack came as its staff was trying to help about 150 people aboard a rubber boat when a speedboat suddenly arrived during their first aid mission.

The speedboat – marked as a Libyan Coast Guard vessel, they said – pulled up to the migrants’ inflatable craft and began beating the occupants with sticks. Most of the migrants tumbled into the sea as the boat collapsed during the chaos.

Sea Watch said up to 120 people were taken aboard their vessel and rescued, but in addition to the four fatalities there were an unknown number of missing migrants.

The group demanded an inquiry into the incident, which they claim was “the latest incident of alleged Libyan official units” endangering migrants and the search-and-rescue humanitarian workers.

Sea Watch monitors migrant routes on the Mediterranean to support safe passage in waters off Libya and Greece, but does not transport migrants and refugees themselves. Volunteers scan the waters for boats in distress or, when migrants are located by the Maritime Rescue Coordination Centre (MRCC) in Italy, launch their own boats to provide water, life vests and medical assistance until further help arrives.

Sea Watch crews were not seriously injured, though their own boat also was attacked, they said.

Image: Sea Watch