At least four people have been killed after an Israeli navy patrol fired on a group of Palestinians in Nuseirat off the Gaza coast.

Medical sources told Al Jazeera that those killed on Monday were fishermen, but the Israeli navy claimed they were divers planning a "terror attack".

"An Israeli naval patrol spotted a boat with four men in diving suits on their way to carry out a terror attack and fired at them," an Israeli military statement said.

Hamas security sources confirmed finding four bodies and said a fifth man was missing, presumed dead.

'Gunshots to head'

Four bodies were retrieved and taken to a hospital in central Gaza, two of the dead had suffered multiple gunshots to the head, Moawiya Hassanain, a Palestinian health official, said.

The incident came a week after nine pro-Palestinian activists were killed in a clash with naval commandos as their vessel tried to reach Gaza.

Israel has been enforcing a blockade of Gaza since 2007, when Hamas seized the territory.

The closure also includes a maritime blockade that was highlighted in recent days when Gaza-bound aid ships were intercepted by the Israeli navy.