A 19-year-old Israeli Jewish man was arrested in Israel Thursday as the primary suspect in a string of bomb threats targeting Jewish community centres and other institutions in Canada and the U.S.

Israeli police spokesman Micky Rosenfeld described the suspect as a hacker, but said his motives were still unclear. Israeli media identified him as an American-Israeli dual citizen and said he had been found unfit for compulsory service in the Israeli military.

"He's the guy who was behind the JCC threats," Rosenfeld said, referring to the dozens of anonymous threats phoned in to Jewish community centres in North America, as well as Australia, New Zealand, and in Israel over the past two months.

In Canada, threats have been made recently to Jewish community centres in Vancouver, Calgary, Winnipeg, Toronto and London, Ont.

The U.S. Anti-Defamation League says there have been more than 120 bomb threats against U.S. Jewish community centres and day schools in the U.S. since Jan. 9. Those threats led to evacuations of the buildings, upset Jewish communities and raised fears of rising anti-Semitism. The threats were accompanied by acts of vandalism on several Jewish cemeteries.

The threats led to criticism of the White House for not speaking out fast enough. Last month, the White House denounced the threats and rejected "anti-Semitic and hateful threats in the strongest terms."

U.S. Attorney General Jeff Sessions says the arrest shows the Justice Department will not tolerate religious-oriented attacks.

Sessions said in a statement Thursday that the arrest is the result of a large investigation into hate crimes against the Jewish community. He says the Justice Department "will not tolerate the targeting of any community in the country on the basis of their religious beliefs."

He called work by the FBI and Israeli police "outstanding."

'JCCs are safer today than ever before': CEO

In a statement, JCC Association of North America president and CEO Doron Krakow applauded the work of law enforcement and emphasized the group's community centres are safe.

"We are gratified by the progress in this investigation, and applaud the commitment and leadership of the FBI and other federal agencies, Israeli law enforcement, and local law enforcement across the United States and Canada," said Krakow.

"Throughout this long running period of concern and disruption that we are hopeful has come to an end, JCCs have had the opportunity to review and assess our security protocols and procedures, and we are confident that JCCs are safer today than ever before."

Hope threats will be over

The head of a Jewish community centre in New Jersey that had been targeted by bomb threats says he's thankful that U.S. and international law enforcement prioritized the investigation and have caught a suspect.Jordan Shenker, head of the Kaplen JCC on the Palisades in Tenafly, N.J., says he is cautiously optimistic that the man arrested in Israel on Thursday acted alone and that the threats will be over.

Shenker says the arrest has led to a feeling of being able to exhale, but that the centre has always prioritized security and will continue to do so.

U.S. authorities also arrested a former journalist from St. Louis for allegedly threatening Jewish organizations. Juan Thompson has been indicted in New York on one count of cyberstalking.

But Israeli police described the local man as the primary suspect in the wave of threats.

Israeli police said the suspect made dozens of calls claiming to have placed bombs in public places and private companies, causing panic and "significant economic damage," and disrupting public order, including by the hurried evacuations of a number of public venues around the world.

Rosenfeld said the man called Delta Airlines in February 2015 and made a false threat about explosives aboard a flight from JFK airport in New York. The threat allegedly led to an emergency landing.

Hacker phoned via computer network

Rosenfeld said the man, from the south of Israel, used advanced technologies to mask the origin of his calls and communications to synagogues, community buildings and public venues. He said police searched his house Thursday morning and discovered antennas and satellite equipment.

"He didn't use regular phone lines. He used different computer systems so he couldn't be backtracked," Rosenfeld said.

Yaniv Azani, head of technology in the Israeli police's cyber unit, says the man used "several different means to camouflage the various layers of communication mechanisms" to carry out the calls.

Nimrod Vax, co-founder of U.S.-Israeli cybersecurity firm BigID, says the phone calls required a certain level of sophistication, but were "not too difficult" for an experienced hacker

After an intensive investigation in co-operation with FBI representatives who arrived in Israel, as well as other police organizations from various countries, technology was used to track down the suspect, Rosenfeld said.