Image copyright Getty Images Image caption A Las Vegas area JCC is searched for bombs after a suspicious phone call

The US Department of Homeland Security has offered help to Jewish Community Centers after they received more than 100 hoax bomb threats in recent weeks.

Secretary John Kelly called upon his agency to "heighten our outreach and support", to Jewish institutions following the spate of attacks.

Jewish cemeteries have been desecrated in Philadelphia and St Louis.

President Donald Trump has condemned these attacks and the murder of an Indian in Kansas as "hate crimes".

Mr Kelly said his office had spoken on Wednesday to the Jewish Community Center (JCC) Association of North America, which represents more than 150 campuses.

The JCC, which offers athletic and educational programmes, has faced severe disruption amid repeated building evacuations.

No arrests have yet been made, and authorities have not released any information about motive.

Media playback is unsupported on your device Media caption "It's other people's loved ones - you don't do this": People gather at Philadelphia graveyard

During the discussion, the DHS offered assistance from their liaisons, who have offices in all 50 US states.

They also offered access to federal assistance, including "facility vulnerability assessments and "active shooter preparedness and bombing prevention training".

Over the past 18 months the agency has held active shooter drills with Jewish organisations in California, Virginia, New Jersey, and Florida, with more planned in the coming months.

Image copyright AP Image caption Hoax bomb threats have triggered evacuations, causing mass disruption at JCC's

Israel's Jewish Agency, the world's largest Jewish non-profit organisation, has expressed "deep concern" over the anti-Semitic threats.

"I trust that US authorities will act resolutely to find those responsible, bring them to justice, and prevent such incidents from recurring", the agency's chairman Nathan Sharansky said.

Israeli Prime Minister Benjamin Netanyahu applauded Mr Trump: "World leaders need to unequivocally condemn anti-Semitism wherever it is found.

"And I appreciate the fact that in the last few weeks and days, President Trump and Vice President Pence have taken a strong stance in condemning anti-Semitism."

Image copyright ABC Image caption Some 170 headstones were damaged at a Jewish cemetery in St Louis, which was established in 1893 by a group of Russian immigrants

Hundreds of Jewish headstones were toppled over in Philadelphia and St Louis, leading to interfaith fundraising drives to repair the damages.

Several Muslim military veterans have taken to Twitter to offer to protect Jewish institutions.

A rally to "Stand Against Hate" is being held in Philadelphia on Thursday at Independence Hall, where the US Constitution was signed.

The Jewish Federation of Greater Philadelphia says the event is intended to "restore a sense of security and peace to our community".