Assailants have broken into the offices of two Gaza newspapers with ties to opposition groups in the Strip, and the Palestinian journalists' union on Saturday held the ruling Hamas responsible for the burglaries.

Equipment worth thousands of dollars was taken Friday from the offices of Al Istiqlal, a weekly affiliated with the militant Islamic Jihad group, and from Al Watan Voice, an online publication tied to the Fatah movement of Palestinian Authority Chairman Mahmoud Abbas.

Hamas, which won parliament elections in 2006, briefly governed jointly with Fatah, but then took control of Gaza by force in June. Since then, Hamas loyalists have ransacked key Fatah offices, seizing equipment and documents.

Islamic Jihad is close to Hamas in ideology, but there have been signs of friction since June, over Hamas' assertion that it is the sole ruler of Gaza and will not permit other groups to carry weapons in public.

The Palestinian journalists' union said in a statement Saturday that it held Hamas supporters responsible for the break-ins at Al Watan and Al Istiqlal.

"We call on them to stop the ongoing assault against the media and freedom of speech," the statement said. "The union said the two burglaries are part of systematic attacks on journalists in Gaza, with the aim of silencing the press."

Hamas government officials were not immediately available for comment.