The Islamic Movement in Israel has radicalized sections of the population, driving away secularism from Arab villages and towns and replacing it with an Islamist grassroots movement that - like Hamas - is linked to the global Muslim Brotherhood network.
"Keeping tabs on them is a sensitive matter," a law enforcement source told The Jerusalem Post on Tuesday.
"The Shin Bet [Israel Security Agency] is responsible for gathering intelligence on the Islamic Movement. This is the case for all forms of political subversion," the source continued. "If the Shin Bet receives information that points to an imminent disturbance of the peace, it passes the intelligence over to the Israel Police."
Police and Shin Bet officials hold regular meetings to analyze the current situation and share information on the Islamic Movement. Police poured over the latest inflammatory rhetoric from Raed Salah, the head of the movement's northern wing and concluded that he had crossed the line from legitimate free speech to illegal incitement to violence and arrested him on Tuesday.
Despite the movement's dangerous influence, calls to ban it are not in tune with Israel's democratic nature, said former police inspector-general Assaf Hefetz.
"In a democratic state, we cannot simply ban a movement. That is very extreme," Hefetz said.
"What we must do is act when it violates the law, and prevent it from exploiting democratic freedoms to work against our democracy," he added. "We must limit their ability to act, not through legislation, but through law enforcement."
The Islamic Movement's tendency to throw fuel on the fire of Arab-Jewish tensions dates back many years. Salah was accused by the Orr Commission - set up to investigate the October 2000 Israeli Arab riots - of praising violent acts and demonizing the State of Israel in his speeches.
In 2003, Salah and a number of other suspects from the Islamic Movement's northern branch were convicted of abetting Hamas, communicating with a foreign agent, and membership of a terrorist organization. Salah was imprisoned for a year and a half.
In 2007, Salah cited anti-Semitic blood libels in his speech, accusing Jews of using blood in the preparation of foods.
This past June, he addressed Muslim students at the University of Haifa who are members of an Islamic-Movement-affiliated group on campus known as IKRA, and claimed that Prime Minister Binyamin Netanyahu was seeking to "build the Temple" on the Temple Mount.
Calls for Muslims to rally to protect the Temple Mount from so-called "Jewish threats" have become a staple of Salah's rhetoric.