The plot was claimed hours after Abbas called off a trip to Gaza for talks aimed at reaching a definitive ceasefire between fighters from his Fatah party and Hamas that has left nearly 50 people dead and 100 wounded since Sunday.

"Abu Mazen's (Abbas's) visit to Gaza was cancelled after the discovery of a tunnel under Salaheddine Road full of explosives placed by the Ezzedine al-Qassam Brigades to blow up (his) convoy," said a senior security official, referring to Hamas's military wing.

"The explosives were found on the route that Abu Mazen takes to travel to Gaza," the source added, speaking from the Palestinian political capital of Ramallah in the West Bank.

An official in Abbas's office confirmed the report but Abu Obeida, spokesman for the Hamas armed wing, told AFP "these reports are aimed at poisoning the atmosphere in Gaza. We deny them completely."

Earlier, a source close to the president told AFP that Abbas did not want to go to Gaza until he was sure Hamas was firmly committed to the latest truce, which had already given way to fighting.

As the Palestinian crisis worsened, Israeli aircraft carried out four air strikes on Gaza, killing five people in retaliation for rockets being fired on Israel from the territory.

The first attack hit the headquarters of a Hamas paramilitary force, killing one person and wounding 30. Barely two hours later, a Hamas fighter was killed when Israel fired on a car in Gaza City.