The largest Muslim advocacy organisation has reported that one mosque has received a threatening message from an unknown caller who said in a voice mail: "We will do to your people what you did to them," referring to the victims of the Dec. 2 San Bernardino shooting.

The Council on American-Islamic Relations (CAIR) pleaded with the public not to generalise all Muslims as terrorists in the wake of the latest mass killing in the U.S.

"We condemn this horrific and revolting attack and offer our heartfelt condolences to the families and loved ones of all those killed or injured," said CAIR-Los Angeles Executive Director Hussam Ayloush. "The Muslim community stands shoulder to shoulder with our fellow Americans in repudiating any twisted mindset that would claim to justify such sickening acts of violence."

Ibrahim Hooper, spokesman for CAIR in Washington D.C., implored the public not to "generalise from the acts of individuals to an entire faith community," reported Al Jazeera.

The shooting killed 14 people and was carried out by Muslim couple Syed Farook, 28, and Tashfeen Malik, 27. They were heavily armed with guns, bombs, and ammunition.

Hooper also protested the New York Post's headline that described the two dead suspects as "Muslim Killers." The Ruper Murdoch-owned newspaper later changed it.

"It's completely outrageous that the New York Post would use that front-page headline," said Hooper as he called the newspaper "irresponsible" but said he was not surprised as "it is known for its anti-Muslim bigotry."

"It's inflammatory and we believe it incites hatred against all Muslims, and not just against the people who allegedly carried out the San Bernardino attacks," he said.

The CAIR has called on state and federal authorities to investigate as a hate crime a phone threat to a Virginia mosque.

The Manassas Mosque in Manassas, Virginia, received the threat on its voice mail last night Wednesday.

The caller who said he represents the "Jewish Defense League" referred to the California killings and said that the group "will do to your people what you did to them."

"Just as we condemn the horrific killings in San Bernardino, we as a nation must repudiate threats to all American houses of worship," said Hooper. "We call on state and federal law enforcement authorities to investigate this threat as a hate crime and to bring the perpetrator to justice."

The mosque's imam, Abu Nahedian, received the phone threat that was forwarded to his personal phone.

Last year, the mosque was also vandalised.

He blamed lack of education and awareness about Islam for the threat but said educated people "know that we [Muslims] are the also victims" of violence.

Nahedian said worshippers at the mosque were subjected to verbal abuse and other threats even before the San Bernardino shooting.

"This is part of our life anyway. But we always teach the congregation to be kind to people, and to let your action be the defender of your faith," he said.