Three California mosques received threatening letters last week in which Muslims were called the "children of Satan" and were told that President-elect Donald Trump will "cleanse America" starting with Muslims.

Members of the Muslim community are told in the letter that their fate will the the same as "what Hitler did to the Jews."

The letters, received by Islamic centers in San Jose, Long Beach and Claremont, were publicized by the Council on American-Islamic Relations, a national Muslim advocacy organization. A fourth letter was received at an Islamic center in Savannah, Georgia.

Executive Director Hussam Ayloush of CAIR Los Angeles told the L.A. Times that the Long Beach and Claremont centers received the letters on Wednesday but did not go public with them until they'd heard of the letter received in San Jose. All the Islamic centers received identical photocopies of a handwritten sheet of paper, signed by people calling themselves "Americans for a Better Way."

Ayloush told the Times that mosque members were "disheartened that anyone would address fellow Americans, fellow human beings, in such a hateful, dehumanizing way."

Police in San Jose and Los Angeles are treating the letters as incidents of hate crime. The Southern Poverty Law Center reported 51 anti-Muslim incidents in the week following the Nov. 8 election. FBI crime statistics showed 257 bias crimes against Muslims in 2015, up from 154 in 2014.

"Hate crimes are more than just attacks on an individual, they terrorize communities," Los Angeles police Chief Charlie Beck said at a Nov. 23 press conference. "The LAPD is committed to protect and celebrate our diversity, because those differences are what makes Los Angeles a dynamic and vibrant city."

At the Long Beach Islamic Center, Annenberg Media spoke with Chairman Tarek Mohamed, leader of the center.

In the Muslim religion, "one of the most beautiful things a believer can do … is spread peace in the community," he said. It doesn't make sense to attack members of a religion built on peace, the chairman added.

Reach Senior News Editor James Tyner here, or follow him on Twitter.

Executive Producer Lauren Day contributed to this report.