Facebook apologised Monday after temporarily disabling accounts linked to two Palestinian news sites critical of Israel, a move that drew concern over potential online censorship.
Facebook pages of a number of editors of Quds News Network were suspended for several hours last Friday, a campaigner said, in what the social media giant later called a "mistake".
Pages linked to the Shehab News Agency were also disabled, an editor there said.
Quds has 5.2 million likes on Facebook, while Shehab has 6.35 million.
"The pages were removed in error and restored as soon as we were able to investigate," Facebook said in a statement.
"Our team processes millions of reports each week, and we sometimes get things wrong. We're very sorry about this mistake."
The US-based company did not respond to a request for more details on what prompted the closures.
Israel has been in discussions with Facebook to stop what it calls online incitement, including at a meeting of top officials earlier this month.
The country's justice and public security ministers are also seeking legislation banning the use of Facebook to advance "terror" and outlawing incitement from the Internet.
Israeli authorities say such incitement is a main cause of a wave of Palestinian knife, gun and car-ramming attacks over the past year.
Palestinians say they fear the Israeli campaign will lead to censorship of legitimate information and suspect last week's closures were linked to it.
Activists called on Palestinians to boycott Facebook activity for two hours on Sunday in protest. The hashtag #FBCensorsPalestine was also being used on Twitter.
"We fear that Facebook will assist the occupation and close the only space for free expression for the Palestinians," said Iyad al-Rifai, spokesman for a campaign against such closures.
Hussam al-Zaygh, managing editor at the Gaza-based Shehab, called the closures "a political decision dictated by the Israelis".
"It is our right as Palestinian journalists to make our voice heard," he said.
Israeli and American victims of Palestinian attacks filed a $1-billion lawsuit against Facebook in July over allegations it was used by the Palestinian Islamist movement Hamas to organise violence.
Facebook has also faced criticism over censorship in other parts of the world in recent months.
It backtracked a couple of weeks ago on a decision to censor an iconic Vietnam War photo of a naked girl escaping a napalm bombing, after its block on the historic image sparked outrage.
The company is also due to go on trial in France, where a schoolteacher accused it of censorship for blocking his account after he posted a photo of a painting by 19th-century master Gustave Courbet called "L'Origine du Monde" (The Origin of the World) that depicts a woman's vagina.
Earlier this year, a Danish lawmaker also complained that Facebook had removed her picture of the Copenhagen statue of the Little Mermaid because of its nudity rules.