Two fighters have been killed apparently by Israeli army gunfire in the Gaza Strip, Palestinian sources say.

The two Palestinians were killed early on Saturday in the Juhr al-Deek district of Bureij refugee camp in central Gaza, Muawiya Hassanein, director of the local emergency services, told Al Jazeera.

Palestinian witnesses said an explosion occurred when the fighters attempted to fire a mortar round towards Israel.

Fierce clashes had erupted between Palestinian fighters and Israeli soldiers on Friday when Israeli forces attempted to raid the area, Al Jazeera's correspondent in Gaza, said.

The Israeli military denied any firing in the area but said that two mortar rounds were launched from Gaza overnight.

No Palestinian faction has claimed the dead fighters as its members.

Israeli forces have repeatedly raided areas in the east and south of Gaza during the past few days.

Attacks by Palestinian groups in Gaza and Israel have continued despite separate unilateral ceasefires declared on January 18.

The ceasefires followed Israel's 22-day offensive in Gaza during which about 1,300 Palestinians were killed.

Thirteen Israelis died during the same period due to the offensive or because of Palestinian rocket fire into Israel.