The union is dominated by the secular Fatah movement, which Hamas drove out of Gaza when it seized power in June 2007.
The Hamas-run interior ministry had no immediate comment on the incident.
Najar, who is based in the West Bank town of Ramallah, said the raid was the latest in a series of "violations of the rights of the media" in Gaza, adding that around 25 media outlets had been shut down since the Hamas takeover.
He said the syndicate would immediately contact the Arab journalists union and international organisations over the alleged violations.
The Palestinian union held elections almost a year ago, in which all the main Palestinian factions took part except for Hamas and Islamic Jihad.
Hamas and its Fatah rivals, who dominate the Western-backed Palestinian Authority, have been fiercely divided since 2007, with both sides accusing the other of jailing and mistreating political opponents.
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The Hamas-run interior ministry had no immediate comment on the incident.
Najar, who is based in the West Bank town of Ramallah, said the raid was the latest in a series of "violations of the rights of the media" in Gaza, adding that around 25 media outlets had been shut down since the Hamas takeover.
He said the syndicate would immediately contact the Arab journalists union and international organisations over the alleged violations.
The Palestinian union held elections almost a year ago, in which all the main Palestinian factions took part except for Hamas and Islamic Jihad.
Hamas and its Fatah rivals, who dominate the Western-backed Palestinian Authority, have been fiercely divided since 2007, with both sides accusing the other of jailing and mistreating political opponents.
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