A blast has ripped through a seaside discotheque in Tel Aviv, killing at least four people and wounding another 50.
Tel Aviv's police chief David Tzur said the attack late on Friday took place at the entrance to the disco, called The Stage.
Islamic Jihad, Hamas and al-Aqsa Martyrs Brigades - an offshoot of the mainstream Fatah movement - all have denied responsibility for the explosion.
Some Israeli security sources have suggested that the Lebanese Hizb Allah might be to blame for the attack, Aljazeera reported on Saturday.
Israeli police have set up checkpoints around Tel Aviv to capture a person who, witnesses say, was with the bomber before the attack, Aljazeera reported.
The Palestinian Authority, which has agreed to a ceasefire with
Sami Abu Zuhri, a spokesman for the resistance group Hamas, said the organisation was "fully observing the period of quiet as we told Abu Mazin (Mahmud Abbas) at our last meeting in
"But the responsibility for this operation lies with the Israeli enemy because even though we are observing this period of quiet, the Israeli aggressions and crimes are continuing."
A senior leader of the Islamic Jihad - another Palestinian resistance group - denied any role in the blast.
"Islamic Jihad is committed to calm in accordance with the understanding it has reached with President Abu Mazin. The Islamic Jihad has no knowledge of the attack in Tel Aviv," Nafidh Azzam said.
Several Palestinians have been killed over the past month after the truce came into effect.
Israeli Public Security Minister Gideon Ezra said
PHOTO CAPTION
An undated picture released by the family shows Abdullah Badran, 21, a Palestinian university student from the nothern West Bank village of Deir al Ghusun who blew himself up, killing four Israelis, at a Tel Aviv nightclub late Friday Feb. 25, 2005. The child he is holding is his nephew, no name available. (AP)