A national Jewish civil rights organization is urging institutions across the United States to ramp up their security efforts amid a wave of bomb threats phoned into Jewish community centres and schools in as many as 12 U.S. states Monday.

The threats to 13 community centres and eight schools were determined to be hoaxes but it’s the fifth such wave of threats this year, raising fears of surging levels of anti-Semitism. In all, nearly 90 bomb threats have been called into Jewish institutions this year, according to the Anti-Defamation League.

The incidents, along with vandalism to Jewish cemeteries and the appearance of graffiti using Nazi swastikas, have left many on edge and calling for President Donald Trump to forcefully speak out against hate crimes.

Jewish community centres and schools in Alabama, Delaware, Florida, Indiana, Maryland, Michigan, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island and Virginia were evacuated Monday, according to the ADL. For some of the targeted schools and centres, this is the third time they’ve had to initiate an evacuation this year.

“While this latest round of bomb threats to Jewish community centres and day schools across the country again appears to not be credible, we are nonetheless urging all Jewish institutions to review their procedures,” said ADL CEO Jonathan Greenblatt.

He said the ADL’s national headquarters also recently received a bomb threat.

He urged Jewish institutions to review bomb protocols from the FBI and Department of Homeland Security, along with safety manuals provided by the ADL. Last month, the organization announced it would convene local security training in partnership with the FBI.

While the ADL focused on security Monday, another national Jewish organization said the community “must see swift and concerted action from federal officials” to find those responsible.

“Anti-Semitism of this nature should not and must not be allowed to endure in our communities,” David Posner, the director of strategic performance at the JCC Association of North America, said in a statement.

“The Justice Department, Homeland Security, the FBI, and the White House, alongside Congress and local officials, must speak out – and speak out forcefully – against this scourge of anti-Semitism impacting communities across the country.”

Attorney General Jeff Sessions called the vandalism and bomb threats serious, unacceptable behaviour and said the department will "do what it can to assist in pushing back ... and prosecuting anybody that we can prove to be a part of it."

"We are a nation that is a diverse constituency, and we don't need these kind of activities," Sessions said.

White House press secretary Sean Spicer said Monday the investigations will be handled by law enforcement at the state and local level and that comment about what additional steps can be taken should come from the justice department.

“One of the things we can do is speak from this podium in particular and other places to make sure every American understands what our values are and that that kind of behaviour and activity is wrong and won’t be tolerated and the highest levels of government denounce it.”

In a tweet Monday, Hillary Clinton said: “With threats & hate crimes on rise, we shouldn’t have to tell @POTUS to do his part. He must step up & speak out.”

Clinton, the Democratic presidential nominee who lost to Trump in November, attached a story to her tweet about the widow of the victim of an apparently racially motivated attack in Kansas.

For his part, Trump has said he is the “least anti-Semitic person” in the world, noting his daughter Ivanka and her family are Jewish. But many Jewish groups say the president has not done enough to condemn white supremacists who lined up behind him during the campaign.

Trump also raised questions when his Holocaust Remembrance Day statement in January did not mention the six million Jewish victims of the Nazi regime.

The executive director of the Anne Frank Center last week accused Trump of being a “purveyor” of anti-Semitism who did not immediately address the rising tide of bomb threats and vandalism.

A national meeting of the ADL last fall was preoccupied with discussions of the rise of anti-Semitic imagery and harassment of Jews on social media and the apparent re-emergence of age-old anti-Jewish conspiracy theories thanks to the alt-right.

More than 100 headstones were vandalized at a Jewish cemetery in Philadelphia over the weekend, following vandalism to more than 150 headstones in suburban St. Louis less than a week before.

Vandalism featuring Nazi swastikas has also occurred in Miami Beach and Rhode Island in recent days. But it’s not limited to the United States. Police are also investigating disturbing incidents in Montreal, Toronto, Hamilton and Squamish, B.C. over the last week.

Philadelphia Mayor Jim Kenney says authorities there are doing everything possible to find those "who desecrated this final resting place."

The ADL and a police union are offering a $13,000 reward for information leading to the arrest and conviction of those responsible. A local building trades union is offering to repair the cemetery for free.

A Muslim crowdfunding effort to support the cemetery in Missouri has raised more than $136,000, and organizers say they will use some of the money for a Philadelphia cemetery where similar vandalism occurred.

The money raised so far is nearly seven times more than the original $20,000 goal and will be used to  repair damage and upgrade security.

-With files from The Associated Press