Internal Palestinian fighting spread to northern Gaza as Hamas militants opened fire on the Fatah security building in the town of Beit Lahiya, setting it ablaze. Hamas forces raided a Fatah military intelligence post. Hamas said their forces came under fire first. 10 people, including six Fatah policemen were wounded, in overall clashes in the northern Gaza Strip. Elsewhere in central Gaza, Hamas militants took control over an armoured vehicle which was hit earlier when Hamas gunmen ambushed what the group said was a convoy carrying weapons to Mahmoud Abbas's presidential guard in the Gaza Strip. Abbas's Fatah faction said the four-truck convoy, which crossed into Gaza from Israel, was carrying medical equipment and tents, and accused Hamas of plunging a 3-day-old ceasefire into ''grave danger.''