A Palestinian news agency said that a firebomb was hurled at its Gaza City newsroom, setting off a small fire Sunday morning.
No one claimed responsibility for the fire at the Maan news agency, which damaged the front door of the office but did not spread beyond.
Maan editor-in-chief Nasser Laham decried the firebombing as an assault on "freedom of the press in Palestine." The Palestinian Journalists Syndicate called it "an attempt to silence the free press" and urged authorities to investigate.
Maan is an independent news agency but critics accuse it of being sympathetic to the Palestinian Authority that rules the West Bank.
Several months ago an explosive device was planted in front of the same office.
Police in Hamas-ruled Gaza have investigated that attack, but nothing has emerged.
The New York-based Human Rights Watch has accused Palestinian security forces in both Gaza and the West Bank of harassing journalists investigating corruption or seen as supporting critics.