ROME (Reuters) - An American naval vessel went to the aid of a rubber boat that was sinking off the coast of Libya, rescuing 41 people and collecting 12 bodies, a humanitarian group said on Tuesday after its ship was contacted by radio to help out.

The U.S. navy vessel Trenton called the German charity Sea Watch, which operates the only charity rescue ship currently on patrol off the Libyan coast, to alert them to the shipwreck and ask for assistance, a spokesman for Sea Watch said.

The Dutch-flagged Sea Watch 3 ship was en route to rendezvous with the Trenton, said spokesman Ruben Neugebauer. It was not yet known how many people were on the boat before it started sinking.

“This shows what happens when there are not enough rescue assets at sea,” Neugebauer told Reuters. The Aquarius rescue ship will be gone for some 10 days as it takes migrants to Valencia, Spain, after it was refused a port in Italy or Malta.

“This shipwreck shows that we are needed,” he added, saying the American vessel probably called Sea Watch because “there’s just nobody else out here. We’re the only asset at the moment.”

There was no immediate comment from the U.S. Navy.