By Andrea Shalal

BERLIN (Reuters) - A German-based humanitarian group said on Tuesday up to 30 African migrants may have died because of what it called "aggressive" Libyan interference in a rescue operation outside Libyan territorial waters.

The Sea-Watch group released new photographs of Friday's incident, including one showing a Libyan coast guard vessel pulled up next to the migrant boat and another of a crew member in military uniform aboard the rubber dinghy.

Spokesman Ruben Neugebauer said Sea-Watch crew members observed at least one Libyan coast guard member kicking and hitting migrants with an undefined object, possibly a stick or cable, and spurring some migrants to panic and jump overboard.

He said the Libyan vessel also rammed one of the dinghy's two rubber tubes, causing it to rapidly deflate and dump the estimated 150-160 people on board into the Mediterranean.

A spokesman for the Libyan naval forces in Tripoli said on Saturday its crew boarded the rubber dinghy but denied that the migrant boat was attacked.

Aided by people smugglers based in Libya, some 150,000 people have set off for Italy in unseaworthy boats so far this year, with more than 3,740 having died or disappeared during the crossing of the southern Mediterranean.

Since Friday alone, more than 6,000 men, women and children have been rescued at sea.

Sea-Watch said the Libyan coast guard boat sped off at high speed with its lights off after the migrants - all men plus a few boys from sub-Saharan Africa - began to jump overboard.

"Our crew did everything to save as many lives as possible, but unfortunately, we have up to 30 casualties," Neugebauer told Reuters after a Sea-Watch news conference.

BODIES FLOATED OUT OF REACH

Sea-Watch crew brought four corpses on board, but were unable to retrieve many others that floated away, he added.

Libyan naval forces said the incident occurred in Libyan territorial waters, which end 12 nautical miles from the coast.

Sea-Watch released detailed course charts which it said showed the migrant boat was at least 14 nautical miles off the North African state's coast.

Neugebauer said the Libyan coast guard vessel also carried out aggressive maneuvers to separate the Sea-Watch rescue ship from the migrant boat, preventing crew from handing out life vests and flotation devices.

Communication failed due to language barriers, although the Libyan forces shouted "migrants," and "out, out," gesturing at Sea-Watch to leave the area, the group's report said.

Migrant rescues are often complicated in Libya by the U.N.-backed Tripoli government's struggle to impose its authority on a country where hundreds of armed militias flourish.

German military officials and rescue groups cite numerous incidents in which militias posing as coast guards interfered with rescues or tried to remove motors from migrant boats.

EU military officials are due to start a two-month training for up to 100 Libyan coast guard personnel this week to teach basic skills such as navigation, seamanship, dealing with fire and other risks on board, maintenance, search and rescue, and working with naval forces from other countries.

Sea-Watch planned to continue carrying out rescues as needed, but was weighing its options for the future.

"We are angry that the European Union forces us to go out there again and again," Neugebauer said. "If the whole burden stays on civilian (humanitarian) organizations, this is simply a task we cannot take."

(Reporting by Andrea Shalal; editing by Mark Heinrich)