Image copyright Reuters Image caption The teenager, covering his face, appeared in court on Thursday

Israeli police say a 19-year-old man with American and Israeli citizenship is suspected of making threats against Jewish institutions worldwide.

Police arrested the suspect in the south of Israel on Thursday morning over threats against Jewish communities in the US, New Zealand and Australia.

He was detained by Israeli cyber-fraud police, after an inquiry with the FBI and other law enforcement agencies.

Last month an ex-US journalist was arrested for several of the threats.

Investigators say that 31-year-old suspect's alleged calls were part of a bizarre campaign against a former girlfriend.

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But Israeli police spokesman Micky Rosenfeld said on Thursday the latest suspect's motives are unclear.

In one of the threats made against a Jewish Community Center (JCC) on 18 January, a caller is heard saying: "In a short time, a large number of Jews are going to be slaughtered.

"There's going to be a bloodbath that's going to take place in a short time."

Doron Krakow, president of the JCC Association of North America, said he was "troubled" to hear the suspect is Jewish, adding that he is "hopeful" that the threats have come to an end.

Investigators say the Israeli teen used camouflage technologies to disguise the origin of the dozens of calls.

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

Image copyright Reuters Image caption More than 120 threats have been made against Jewish centres in 2017

In the US, more than 120 hoax bomb threats have been made against Jewish schools, synagogues and cultural centres since earlier January, according to the Anti-Defamation League.

There have also been at least three vandalism attacks made against US cemeteries in recent months.

The teen is also suspected of making threats against Delta Air Lines, forcing a plane to make an emergency landing in 2015 in order to be searched for explosives.

Israeli's minister of public safety Gilad Erdan congratulated the police for the arrest.

"We hope that this investigation will help shed light on some of the recent threats against Jewish institutions, which have caused great concern both among Jewish communities and the Israeli government," he said in a statement.

There is a court order in place preventing the media from reporting the man's name.

He will be held under arrest until 30 March, the court ruled.

Media playback is unsupported on your device Media caption The BBC spoke to a Muslim-American couple targeted by an abusive caller

According to Israeli newspaper Haaretz, the army had refused to draft him on personal grounds, after determining that he was unfit for service.

A reported spike in anti-Jewish incidents led to criticism of the Trump administration, with some saying they did not react quickly or forcefully enough to the hate threats.

Last month, the White House denounced the threats and rejected "anti-Semitic and hateful threats in the strongest terms".

Earlier this month the Department of Homeland Security condemned the "unacceptable and disturbing rise in the number of apparent hate-inspired attacks and harassment against individuals and communities".

It pledged to provide "support to groups affected by these incidents to enhance public safety".