General Musa Arafat, the head of Palestinian intelligence in the West Bank and Gaza City, issued a statement after his office was blasted by a rocket-propelled grenade which injured at least 13 Palestinians.
The RPG was launched at the Palestinian Authority's main security centre in central Gaza.
General Arafat who is a cousin of Palestinian President Yassir Arafat issued a statement calling the attack a "failed assassination attempt by unknown people".
The RPG caused some damage to the police intelligence building, a nearby prison, also inside the compound, sustained the brunt of the damage.
Prisoners were among the 7 wounded, medical sources said. One was said to be in serious condition, but most suffered only minor injuries.
Three Palestinians were arrested for questioning, security sources said. The reasons for the attack were unclear.
An Israeli military source was quoted as saying the explosion was an "internal Palestinian matter."