Militants detonated a bomb at the entrance to the bureau of al-Arabiya television channel on the 12th floor of a Gaza City building, witnesses said.
No injuries were reported and security officials said no one was inside the bureau at the time.
Reporters and office employees had received telephone threats from unknown individuals several days ago.
Police and security services have started investigations into the bombing, which was condemned by reporters as "a very dangerous action against journalists and journalism".
One week ago, the station broadcast a recording of Prime Minister Ismail Haniya saying: "Even if Allah (god) gave us orders, we would never make concessions."
A spokesperson for Haniya's Islamic Hamas movement denied that he had made such statements and condemned the channel for giving the impression that the premier had blasphemed. The movement vowed to sue the Dubai-based channel.