Libyan authorities fired warning shots in the air and pointed mounted guns at rescuers and migrants, according to the humanitarian group Sea-Eye. A group spokesman said the act was unprecedented.
German NGO Sea-Eye said one of its vessels was threatened by masked Libyan security forces who fired warning shots as it rescued 90 migrants from a lifeboat on Saturday.
The crew aboard the NGO ship, named Alan Kurdi, rescued the migrants after receiving a distress call from people aboard the lifeboat off the coast of Libya.
Sea-Eye spokesman Gorden Isler said the Libyan boats arrived as the rescuers were handing life jackets to men and women on a white dinghy off the coast of Libya and began circling the ship, hampering rescue efforts.
He said the masked men fired "warning shots" and pointed mounted guns at the rescue crew and the migrants, some of whom had jumped into the water, before retreating.
Shock at sea
"We are in shock, we have never been threatened in this way," Isler told AFP, adding that EU member states were allowing this "brutal behavior".
"We were able to get 90 people on board, including two women," Isler said.
He added that a pregnant woman rescued from the dinghy may have suffered a
miscarriage during the incident.
Saturday's operation comes a week after 104 people were rescued just off the coast of Libya by the Ocean Viking ship, run by NGOs SOS Mediterranee and Doctors Without Borders.
The route through Libya to reach Europe is a popular path for migrants from East Africa, the Sahel and the Middle East.
Last month, Italy, France, Germany and Malta proposed a system for automatically distributing asylum-seekers across the EU to prevent rescue ships from being stranded at sea.
So far, only a handful of other nations have backed the plan.
law/stb (AFP, AP, dpa)