The intelligence service said its head, Tareq Abu Rajab, was the target of an assassination attempt.

Abu Rajab and six bodyguards and aides were in the lift when the blast went off. Abu Rajab, who survived an assassination attempt two years ago, underwent surgery at a nearby hospital, but doctors refused to disclose his condition. The aides and guards were in a serious condition.

The explosion came at a time of growing tensions between the Hamas government and moderate Palestinian President Mahmoud Abbas.