Two Gaza fishermen were shot dead at sea as the Palestinian fishing union blamed Egypt and demanded an investigation.
Hundreds of mourners on Sunday buried the dead bodies of two brothers.
It was reported that three brothers were fishing on Friday in the Mediterranean Sea off the Gaza Strip, a crowded sliver of land sandwiched between Egypt and Israel, when their boat was hit by gunfire.
Two died and their bodies were returned to Gaza by Egyptian forces, the union said, while the third brother was wounded and remains in Egypt.
Gaza's rulers Hamas also blamed the Egyptian army. There was no immediate comment from Egyptian officials.
As hundreds gathered Sunday in the central Gaza district of Deir al-Balah to bury the men, their mother pleaded with Egyptian President Abdel Fattah al-Sisi to let her surviving son Yasser Zaazoua come home.
"Sisi, you killed two of my sons," said Oum Nidal Zaazoua. "If you have compassion, give me back Yasser who is still in detention."
Israeli security forces, who have imposed a blockade for Gaza for 13 years, say fishing is sometimes used as a cover for smuggling.
Directly south of Gaza is Egypt's Sinai Peninsula, where security forces are battling both clandestine trade and jihadist groups.