Since January this year, the ADL said Jewish centres, schools and ADL offices across America have received at least 140 threats of violence or harassment. It referenced, "at least 98 incidents against JCCs and Jewish Day Schools" in 33 states., as well as the desecration of headstones at multiple Jewish cemeteries.
"This is not 'normal.' We will not be deterred or intimidated", ADL's CEO, Jonathan Greenblatt, said in a statement.
Police say the Miles Nadal Jewish Community Centre in Toronto was evacuated out of "an abundance of caution" in light of threats made in New York, Oregon, Wisconsin, Illinois, Florida, Maryland.
"We've never seen such a period of concentrated threats against the Jewish community", New York Mayor Bill de Blasio told a news conference.
"We take the safety and security of our families, our community, and our staff as a top priority", the email said, adding that "the continuation of these threats across the country to JCCs, other Jewish institutions, and the Boulder JCC is very disheartening". "It is time for action, and we call on the administration and Congress to take concrete steps to catch those threatening the Jewish community".
In Alabama, state Attorney General Steve Marshall on Wednesday condemned the repeated threats at one Birmingham center as "cowardly", and said he would "commit whatever resources and support our federal partners may require to apprehend and bring to justice those responsible".
Spicer called the incidents "anti-Semitic hate crimes" and said the White House denounces them "in the strongest terms".
Meanwhile, New York Gov. Andrew Cuomo said the state police would investigate bomb threats that forced evacuations Tuesday at two Jewish community centers upstate. "We are working with the Federal Bureau of Investigation to bring those responsible for these threats to justice".
Last week, five grave stones were found toppled at the Waad Hakolel Jewish Cemetery, also named the Stone Road Cemetery, in the third such occurrence at a Jewish cemetery in a span of a few weeks.
The letter emphasized the impact these threats at all levels, stressing that it impacted both those of Jewish faith and other communities.