A Palestinian suicide bomber has blown himself up at a crossing between Israel and the Gaza Strip, the Israeli army has said.
Al-Aqsa Martyrs Brigade and Hamas have claimed the attack
An Israeli border policeman was killed and three others were injured in the explosion at a terminal leading to the Erez industrial zone.
Hours later, the Hamas leader in Gaza was reported to have been seriously injured in an attack on his vehicle.
Early reports suggest Abdel Aziz Rantissi's car was hit by missiles.
Thousands of Palestinians are employed at the Erez zone.
The crossing has frequently been attacked by Palestinian militants and security there has been intensified.
In January, a female suicide bomber killed four Israelis after tricking her way into an office terminal at the crossing.
The militant Hamas group and the Al Aqsa Martyrs' Brigades claimed joint responsibility for the latest attack.
They identified the bomber as Fadi Al-Amoudi, 22, from nearby Beit Lahiya.
It was the first suicide bombing since Israel killed Hamas's spiritual leader Sheikh Yassin three weeks ago.
Pocket of factories
The incident comes a day after US President George W Bush endorsed Israeli Prime Minister Ariel Sharon's plan to retain some West Bank settlements and block Palestinian refugees from returning to their former homes in what is now Israel.
The move triggered widespread anger among Palestinians, who accused the US of siding with Israel.
Thousands of Palestinians with permits pass through the Erez checkpoint daily to work in the Erez industrial zone or in Israel.
The industrial zone is a sealed-off pocket of factories inside Israel. Palestinians are not allowed to pass from there into Israel proper.
The explosion happened as the bomber was leaving the industrial zone to return to the Gaza Strip, the army said.
The BBC's Peter Greste, at the Erez checkpoint, says taxi drivers at the dusty outpost say they heard a loud explosion from behind the wire and concrete barriers and saw several Israeli ambulances race past.