JERUSALEM — The government of Palestinian President Mahmoud Abbas has moved to silence critics, raising new concerns about freedom of expression in the West Bank.

Abbas' communications minister, Mashour Abu Daqa, said late Thursday that the attorney general's office ordered several websites shut down over the past six months. The sites belong to an Abbas rival, former Gaza strongman Mohammed Dahlan.

Security forces have also arrested four journalists and an anti-corruption activist who have criticized Abbas and other Palestinian officials on Facebook. The Abbas government has also sued two of the journalists and the activist on charges they defamed the president and other senior officials.

Palestinian media in the West Bank are for the most part official or sympathetic to the Palestinian Authority, forcing West Bankers to voice their dissenting opinions on Facebook. But the government fears Facebook's power because of the role it has played in energizing revolts that have toppled long-entrenched regimes in the Arab world.

The West Bank crackdown has been criticized within the Palestinian Authority and in Washington, too.

"We are concerned about any uses of technology that would restrict access to information," U.S. State Department spokeswoman Victoria Nuland said Thursday. "We've had these concerns in other parts of the world, and we wouldn't want to see the PA going in the direction that some of those regimes have gone in."

Abu Daqa, the communications minister, said the shutdown of the websites was "bad for the image of the Palestinian Authority in the modern world."

He also predicted it would ultimately be ineffective because the websites could continue to reach readers by switching to other domains in a cat-and-mouse game with authorities. Abu Daqa is leaving his post, reportedly for personal reasons.

The man behind the websites, Dahlan, has been feuding with Abbas for the past year, calling him a weak leader and accusing him of allowing his sons to profit financially from his rule. Abbas took away Dahlan's bodyguards and expelled him from the Fatah Party, which the president heads.

Dahlan, who has since left the Palestinian territories, has been widely blamed for the militant Hamas group's violent takeover of the Gaza Strip in 2007, when he was security chief there. He has also been accused of illegally enriching himself through corruption.