[T]he only proven survivors were the two sailors sent along to row the boats, Nikolai Sjirokov and Mikail Klimov. They were captured by [Axis] authorities at the end of March, freezing and starving. During the subsequent investigation in the vicinity of the landing site, the [Axis] found human bones, body parts and even a human head. What remained of the bodies could not be identified, and exactly how they died could not be established. Sjirokov and Klimov would eventually be brought to Oslo, where they were presented as cannibals in a press conference[.]
Immediately after the sinking, Kefalas had said, he got onto a raft together with one of the Russian sailors, Liossis and Kostantinidis. The submarine came alongside and called Kefalas and the Russian on board for interrogation. Among other things, the [Axis] wanted to know the name of the ship and retained a lifebuoy with her name on it, presumably as proof of the sinking.
The two men were returned to the raft and were on it when a grenade was thrown. The blast broke the Third Officer’s arm, and both Liossis and Kostantinidis were wounded. The latter died of these wounds on 15 March and was buried at sea.
I found one exception:
The Axis was a little less courteous when it came to the hospital ship Armenia.
ETA: From Waves of Hate, pg. 106: