Although U.S. President Barack Obama has been known to be a champion of political correctness who is always careful with his words, particularly those affecting the Muslim community, never wanting to inflame passions, he unexpectedly found himself being criticised by American Muslims following his address to the nation on the subject of terrorism on Sunday evening.

What angered the followers of Islam was his remark that American Muslims must help "root out" extremists in their midst, Reuters reported.

In Anaheim, southern California, the imams and workers at a mosque said Obama's message was clear: the U.S. government does not trust them.

They said they felt insulted and discriminated against by Obama's request. They asked why the same message is not sent to Christian churches after mass shootings carried out by non-Muslims.

"It is unfair to speak about the Muslim community in this way," said Moustafa Kamel, the imam of the West Coast Islamic Center. "There is a lot of suspicion of the FBI here."

Two men were recently arrested inside the mosque on charges of conspiring to aid Islamist militants. Kamel and other imams described the arrested Islamic State (ISIS) sympathisers as victims of over-zealous law enforcement.

Taher Herzallaj, the manager at the West Coast Islamic Center, said he read the FBI affidavit against the two suspected ISIS supporters arrested inside the moque and questioned why they were arrested.

"They have not said anything here about attacking America or being a threat to U.S. national security," he said. "My guess is they were trying to join ISIS to do something for Syria," he said.

Mohammed Faqih, the imam of the mosque at the Islamic Institute of Orange County, in Anaheim, did not also like Obama's request that imams like him should do more to root out extremists.

"I didn't like that," Faqih said. "In these cases such as San Bernardino, the mosques did not play a role. They [terrorists] are loners who got radicalised at home, in front of the Internet. If we suspect anybody, we call it in straight away to the FBI."

Shakeel Syed, executive director of the Islamic Shura Council of Southern California, questioned why Obama did not go on television asking Christian churches to police themselves for white supremacists after the shooting of nine African-Americans in Charleston, South Carolina in June.

"Asking Muslims to do this is offensive. There is a collective responsibility to address this," he said.

However, Abdallah Soueidan, owner of Al Amir restaurant in Anaheim and an immigrant from Lebanon, said he welcomed Obama's appeal. "We must be more vigilant. And I wouldn't be surprised, or upset, if we came under more surveillance."