Oren Dorell and Kate Shuttleworth

USA TODAY

Corrections & Clarifications: A previous version of this article failed to make clear that the Palestinian Authority only governs portions of the West Bank.

JERUSALEM — Since a spate of attacks against Israelis began in October, authorities have arrested dozens of Palestinians for "incitement" of violence — based on their Facebook posts.

The Israeli military said it charged 60 people since the outbreak of attacks, while the Haifa-based rights group Adallah Legal Center said the number of arrests is closer to 400, including 150 Palestinians in the West Bank and 250 Arab citizens of Israel.

"Incitement to violence on social media is a phenomenon that only recently is gaining traction," said Lt. Col. Peter Lerner, spokesman for the Israel Defense Forces. "Following attacks, many assailants have stated that they were directly inspired by incitement on social media, which led them to carry out the attacks."

As Facebook faces a backlash over alleged liberal political bias in the United States, authorities in Israel and the West Bank have dragged the social media giant into another controversy involving security and free speech.

The teenager accused of stabbing to death Israeli Dafna Meir in front of her young children in the West Bank settlement of Otniel in January said he watched incitement on social media "and then set out to murder Jews,” Lerner said.

A bill pending in Israel’s parliament would lower the threshold for what constitutes "incitement to violence or terror," and would allow more indictments under such charges.

Current Israeli law permits a charge of incitement to violence and terror only when there's proof that such speech could directly lead to violent acts. The proposed law would not require proof that a suspect intended to carry out violence; merely calling for such acts would constitute the charge, punishable by up to five years in prison. Opponents say the law would be a major infringement on freedom of speech.

American dies in Israel stabbing attack

Biden slams Palestinian silence over fatal stabbing

The violence since last fall has resulted in the deaths of 28 Israelis, two Americans and more than 200 Palestinians.

Israel's online dragnet has netted Palestinians and Israeli citizens alike.

Palestinian beautician Majd Atwan, 22, was sentenced May 9 in an Israeli court to 45 days imprisonment and fined 3,000 shekels ($775) for praising a recent bus bombing in Jerusalem. “The news of 20 settlers injured is nice,” she wrote on Facebook. Uniformed officers took her from her home in al-Khader, a village near the West Bank city of Bethlehem, on incitement charges.

“Your occupation to our land does not need ‘incitement’ for our people to revolt,” Majd told the judge during her trial.

Palestinian youth activist Anas Khateeb, 19, an Israeli citizen, was arrested in November and held for more than a month for his Facebook writings after the spate of attacks began. “I’m next in line,” Khateeb wrote. ”Jerusalem is Arab,” and “Long live the Intifada” (uprising).

The Palestinian Authority, which governs portions of the West Bank, has also arrested some people who only criticized the authority and didn't threaten or praise violence.

Keifeh Quzmar, 27, was arrested May 11 by Palestinian Authority police on charges of "disparaging authorities" and was released on bail Sunday. Quzmar was taken into custody at a cafe after posting on his Facebook page the message: "The Muhaberat (Palestinian Intelligence Service) is rotten.”

He faces a likely sentence of 90 days in jail and a fine, according to his brother, Ismat. The Palestinian Authority did not respond to questions from USA TODAY. Facebook also did not immediately respond.

Israeli Jews also have been charged because of their Facebook writings.

In November, Israeli police briefly arrested Hagai Amir — brother of the man who assassinated Israeli Prime Minister Yitzhak Rabin — over a Facebook post threatening President Reuven Rivlin. Amir was sentenced to five days of house arrest.

In 2014, then-Justice Minister Tzipi Livni launched an effort to counter anti-Arab incitement by Israelis on social media after Israeli soldiers posted photos of themselves with their weapons and called for the deaths of Arabs.

Israeli police spokesman Micky Rosenfeld said recent arrest warrants were obtained if someone expressed the intent on social media to carry out violence. Israeli police, using fake profiles, follow the Facebook pages of key Palestinians, creating a virtual surveillance list. Conversation threads on these pages often lead to other pages, where more threats are found, Rosenfeld said.

European and British laws allow for prosecution for certain kinds of online speech, but such arrests in the United States are rare.

The burden of proof for incitement in the U.S. is high, said Stuart Karle, who teaches First Amendment issues at the Columbia University Graduate School of Journalism. U.S. law requires authorities to balance whether illegal action that someone advocates is immediate and probable, Karle said.

"In the case of social media, how probable is it that people are looking at their phones to decide what to do next?" he said.

In Britain, social media posts can lead to prosecution if they “constitute credible threats of violence” to a specific individual or to property, and in cases of hate speech, according to guidelines published by Britain’s Crown Prosecution Service.

The European Commission has held that extreme racist speech is not protected because of its potential to undermine public order and the rights of the targeted minority.

Aaron Sagui, spokesman for the Israeli Embassy in Washington, said authorities in Israel have to balance free speech with security.

“Israel is a country of law and a vibrant democracy that holds in high regard freedom of expression," Sagui said. "As the recent wave of Palestinian terror proves, incitement and the encouragement of terror and murder on social media might end in actual violence. It’s not only our right, but also our obligation to stop the incitement that drives young Palestinians to go out and kill Israelis.”

Dorell reported from Washington, D.C.