At least four Palestinians have been killed after an Israeli navy patrol fired on a group of men allegedly wearing diving gear in Nuseirat off the Gaza coast.The Israeli military said those killed on Monday were planning a "terror attack".

But al-Aqsa Martyrs' Brigades, the armed wing of Fatah, told Al Jazeera the men were members of the group and were only conducting "training exercises".

"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.

 Nicole Johnston, Al Jazeera's correspondent in Gaza, said there were six people on the boat when it came under Israeli fire.

"Four were killed, one escaped - a senior member of al-Aqsa - and one person is still missing. The group presumes he too is dead.

"The men were doing group training exercises, they were not fishing as had previously been reported by Palestinian medical sources that said they were fishermen," she said.

Moawiya Hassanain, a Palestinian health official, said two of the dead had suffered multiple gunshots to the head.

Israel has been enforcing a blockade of Gaza since 2007, when Hamas took control of the territory. The closure also includes a maritime blockade.

PHOTOT CAPTION

Palestinians mourn next to the body of Ibraheem Al-Whadi during his funeral in a mosque in Gaza City June 7, 2010.

Al-Jazeera

'Gunshots to head'