Fifteen Palestinians, including two children and two gunmen, were killed Friday when a pickup truck filled with masked militants and homemade rockets blew up in a Hamas rally in northern Gaza. At least 80 were wounded.

The cause of the blast in Jabalya refugee camp was unclear.

Palestinians tend to the wounded and dead in the street after an explosion during a demonstration in the Jebaliya refugee camp, Sept. 23. (AP Photo/Emilio Morenatti)

Hamas accused Israel of attacking the procession of military vehicles. "We know that our criminal enemy killed our sons today," said Senior Hamas leader Nizar Rayan. He denied that the vehicles carried explosives, saying it only contained plastic models of rockets that could not detonate.

But the Israeli military denied any connection and Palestinian security officials said it was an accident.

Abu Rashad, who was just metres from the explosion, said three militants with two homemade rockets were in the truck's bed. Three or four other militants, who are extremely popular with children, rode inside as teenagers thronged the vehicle, he said.

Palestinians lay injured on the ground, spattered with blood, and a car was found charred and gutted.

Thousands of Palestinians at the rally, attended by some of the top Hamas commanders, stormed into the streets of the camp, carrying the wounded and shouting for revenge.

The Palestinian Interior Ministry issued a statement calling on Hamas "to shoulder its responsibility for these ... explosions instead of making accusations against others."

If an accident, the explosion would be only the latest in a string of deadly mishaps. Six people were killed earlier this month in Gaza City when a Hamas weapons warehouse exploded. Hamas claimed it was an Israeli attack, but an investigation by Palestinian security officials said the blast was an accident caused by the militants.

The explosion occurred shortly after Gaza gunmen fired several rockets into Israel, causing no casualties.

The rockets were a response to an Israeli arrest raid in the West Bank that killed three Palestinian militants.

Palestinian President Mahmoud Abbas condemned the West Bank killings, calling it a "very dangerous step."

Palestinian leaders have said such raids jeopardise a February ceasefire deal and efforts to restart peace talks.

Border control

Hours before the blast, Palestinians officially took charge of a border crossing for the first time, processing thousands of travellers from Gaza into Egypt.

The Rafah terminal, Gaza's only path to the outside world via Egypt, was sealed by Israel before removing its forces. Israel said it would stay shut for six months pending renovations and proof Palestinians could rein in Gaza militants.

But with Israel's consent, the crossing was opened on Friday for 48 hours to Palestinians who study, work or need medical treatment in Egypt or elsewhere.

16-year-old Samar Salem said: "This is my happiest day ever. We are very happy not to see any Jews in the crossing. For the first time, we are coming to the crossing and we are not afraid to be denied access."

Officials said the terminal would be shut from Sunday until Palestinians reached an accord with Israel on how to ensure smooth travel without leeway for arms smugglers.

Travellers at Rafah had to produce a Palestinian identity card or foreign passport to prevent a repeat of the uncontrolled deluge of Gazans into Egypt in the first days after the pullout.