Israel is under a new threat of terrorism by lone-wolf assailants, Prime Minister Benjamin Netanyahu warned on Monday, as police continued to crack down on relatives and neighbors of an East Jerusalem man who rammed his truck into a group of soldiers in the capital Sunday, killing four.

While Israel has dealt with spates of car-rammings and stabbings over the past years, Netanyahu said this attack was differentiated by the fact that the attacker seemed to take action with little to no forethought.

“I think the most important thing to understand is that we are under a new kind of attack by a lone wolf that gets inspiration and decides in a moment to act, in this case with a car-ramming,” Netanyahu said.

On Sunday, 28-year-old Fadi al-Qunbar drove a truck into a group of IDF cadets who were standing in a group after getting off a bus on a popular promenade in Jerusalem. He killed four people and wounded 16 more.

The scene where a truck rammed into a group of Israeli soldiers, killing at least four in the Armon Hanetziv neighborhood of Jerusalem. (Sebi Berens/Flash90)

The scene where a truck rammed into a group of Israeli soldiers, killing at least four in the Armon Hanetziv neighborhood of Jerusalem. (Sebi Berens/Flash90)

No group has claimed responsibility for the attack, although Netanyahu said Sunday from the scene of the attack that “according to all the signs he is a supporter of the Islamic State,” without elaborating further.

The attack was met with a series of preventative and punitive steps ordered by Netanyahu and his high-level security cabinet.

Following the attack, police arrested nine residents of Jabel Mukaber in connection with the attack. Five of them were members of Qunbar’s family, police said.

The neighborhood of Jabel Mukaber, from which multiple terror attacks have originated over the past year, has been encircled by security forces, who placed a cordon on the village and began carrying out security checks on anyone leaving the area toward other parts of Jerusalem.

“The police force continues with increased operational activities in [Jerusalem] at all times, and it will continue to do so as needed,” the police said in a statement Monday.

Police forces checked drivers and searched parked cars and trucks throughout East Jerusalem in an effort to prevent copycat attacks, police spokesman Micky Rosenfeld said.

A composite image of the four Israeli soldiers killed on January 8, 2017 in a truck-ramming terror attack in Jerusalem. From left, IDF Lieutenant Yael Yekutiel, IDF Cadet Shir Hajaj, IDF Cadet Shira Tzur, IDF Cadet Erez Orbach. (Handout photos IDF Spokesperson)

A composite image of the four Israeli soldiers killed on January 8, 2017 in a truck-ramming terror attack in Jerusalem. From left, IDF Lieutenant Yael Yekutiel, IDF Cadet Shir Hajaj, IDF Cadet Shira Tzur, IDF Cadet Erez Orbach. (Handout photos IDF Spokesperson)

An investigation is underway as to how Qunbar managed to make his way on Sunday to the Jerusalem promenade where the soldiers gathered, who owned the truck he drove and whether he planned his attack ahead of time, Rosenfeld said.

Prime Minister Benjamin Netanyahu visits an IDF solider injured in a truck-ramming attack at the Hadassah Medical Center in Ein Kerem, Jerusalem on January 9, 2017. (Kobi Gidon, GPO)

Prime Minister Benjamin Netanyahu visits an IDF solider injured in a truck-ramming attack at the Hadassah Medical Center in Ein Kerem, Jerusalem on January 9, 2017. (Kobi Gidon, GPO)

Police used concrete slabs to block some entrances of Jabel Mukaber, and a police officer checked cars leaving it. Israeli special forces dismantled a mourning tent erected to receive visitors paying respects for Qunbar, who was fatally shot at the scene of the attack. Overnight, police say, Palestinians shot fireworks at Israeli forces at a police post near the neighborhood.

Netanyahu said Monday he had ordered concrete blocks placed at popular bus stops and hitchhiking posts in the West Bank and Jerusalem, in an effort to prevent further lone-wolf terror attacks.

Speaking from Jerusalem’s Hadassah Hospital in Ein Kerem, where he was visiting three officer school cadets wounded in the attack, Netanyahu said they had told him they were eager to return to action.

“It’s simply unbelievable, they told me one thing: ‘Prime Minister, we want to go back to the course, we want to go back into service, we want to continue our mission as soldiers of the IDF,'” he said, calling it the secret to Israel’s success.

That kind of attitude, said Netanyahu, explained why Israel had always prevailed in the war against terror, and would continue to prevail.

Hospital officials said 16 people were wounded in the attack, including one soldier who was still in a coma Monday morning. Several of the injured were released late Sunday and early Monday.

Palestinian media reported that Qunbar was affiliated with the Popular Front for the Liberation of Palestine (PFLP), a secular terror group, but Qunbar’s family insisted he was “religious,” and Israeli intelligence believes he supported the Islamic State terror group.

On Sunday night, the high-level security cabinet decided on a number of steps following the attack, including ordering the Qunbar family home destroyed at the earliest possible time — limited only by possible court appeals available to the family.

Standing family-unification requests by members of the Qunbar family to allow relatives from Gaza to come live with them in Jerusalem will be denied.

A relative shows a mobile phone photo of Fadi Qunbar, 28, outside his home in Jerusalem, Sunday, Jan. 8, 2017. Qunbar was identified as the terrorist who drove a truck into a group of Israeli soldiers, killing four and wounding 16 others (AP Photo/Mahmoud Illean)

A relative shows a mobile phone photo of Fadi Qunbar, 28, outside his home in Jerusalem, Sunday, Jan. 8, 2017. Qunbar was identified as the terrorist who drove a truck into a group of Israeli soldiers, killing four and wounding 16 (AP Photo/Mahmoud Illean)

The cabinet also ordered the security services to detain and investigate anyone found praising or celebrating the attack, after claims surfaced that some residents of East Jerusalem cheered and distributed sweets to passersby after the attack.

It also gave permission for security agencies to place anyone who expresses support for Islamic State in administrative detention, a controversial counter-terror measure that allows the indefinite detention of terror suspects without trial.