Israeli security forces arrested three people in northern Israel accused of plotting attacks for the Islamic State terror group in August, the Shin Bet security service said Thursday.

A fourth, who is currently serve a life sentence in prison, was also charged with joining the organization, Israeli officials said, while three others were charged with aiding the terror cell.

Though Israeli security forces have claimed more than 40 Israeli citizens have traveled to Syria and Iraq to join the Islamic State, this terror cell is the first IS-affiliate discovered within Israel.

The trio, all residents of the town of Yafia near Nazareth, admitted to interrogators they had purchased weapons, trained with them, collected intelligence on military and police sites and had planned on carrying out terror attacks for the Islamic State group, which they had joined.

Muhammad Sharif, 22, and Ahmed Mahajna, 19, contacted two Arab-Israeli IS operatives from Yafia — Muhammad Kilani and Muhammad Kananneh — who had left Israel to join the organization’s fight in Iraq. According to the Shin Bet, Kilani and Kananneh convinced Mahajna and Sharif to set up the IS cell in Israel.

Sharif, Mahajna and the third suspect, Muhammad Jazalah, 23, were already connected to hard-line Salafi jihadis, security officials reported. Under the direction of their friends fighting for the Islamic State, however, the three pledged their allegiance to the terrorist organization, which Defense Minister Moshe Ya’alon declared illegal in September 2014.

Ahmad Ahmad, 26, the fourth man charged with joining the Islamic State terror cell, is currently incarcerated for the 2009 murder of Yafim Weinstein, a Jewish taxi driver from Nazareth Illit.

From prison, Ahmad allegedly assisted the trio in purchasing the illegal weapons they had planned to use to carry out their attacks.

The terror cell had planned to carry out a shooting attack on a military base in the nearby Migdal Haemek area, the Shin Bet said. To prepare for the attack, Sharif, Mahajna and Jazalah made several trips to the base to collect information on patrols and security cameras.

Five Arab-Israelis suspected of being members of an Islamic State terrorist cell in northern Israel. (Shin Bet)

Five Arab-Israelis suspected of being members of an Islamic State terrorist cell in northern Israel. (Shin Bet)

The three Arab-Israelis also planned on throwing Molotov cocktails on police stations and vehicles in Migdal Haemek and Nazareth; to this end, they also cased out the area in preparation for the attack.

And finally, the Shin Bet claimed, they planned on firebombing stores in the area that sell alcohol, as consuming alcohol is forbidden under Muslim law.

One of the illegal weapons discovered by police and Shin Bet agents in Muhammad Sharif's home. (Shin Bet)

One of the illegal weapons discovered by police and Shin Bet agents in Muhammad Sharif’s home. (Shin Bet)

On Sharif’s phone, investigators discovered numerous connections to the Islamic State, including pictures of its leaders and fighters. They also found a video in which Sharif describes how to handle non-believers, demonstrating for the camera how to slit their throats.

Sharif and the other three suspects were already connected to the Salafi jihadism movement, security officials reported.

Three other Arab-Israelis were also charged with assisting the terror cell, but were not suspected of joining the Islamic State, the Israel Police said.

Ibrahim Aljabarah, his brother Ali Aljabarah and Baha Na’aran were all indicted in Nazareth District Court under weapons charges and making contacts for the purpose of crime.

Sharif, Ahmad, Mahajna and Jazalah were indicted Thursday in the Nazareth District Court for contact with a foreign agent, membership to an illegal organization, activity within that organization, weapons charges and criminal association. The investigation was carried out by the Shin Bet and the Israel Police.

Ahmad’s father, 55-year-old Ali Ahmad, was also arrested and interrogated by police, the Shin Bet said.

Last month, an Israeli-Arab mother of five from northern Israel was indicted for trying to join the Islamic State terror group.

Over the past several years, the number of Palestinian and Israeli Arab volunteer recruits has increased among Syrian rebel groups, and the Shin Bet believes that more than 40 Israeli Arabs have joined the Islamic State in the last two years.