Muslim-American groups have blamed what they describe as the mainstreaming of anti-Muslim hate speech for a shooting that killed three people outside a California mosque on Monday, pointing the finger at lawmakers and other right-wing influential figures.

"We are deeply disturbed, but not at all surprised," the Council on American Islamic Relations (Cair) said in a statement. "Hate against American Muslims is completely out of control."

"Numerous politicians have spent the past year claiming that all ‘mainstream Muslims’ should be destroyed, that American mosques and elementary schools should be shut down, and that American Muslims should be expelled from our nation. Just last week, House Republicans held a congressional hearing to fan the flames of hate against American Muslims, their houses of worship and even Muslim school children," the organisation said, referencing the Republican 'Sharia-Free Caucus' on Capitol Hill, which boasts of more than 60 lawmakers in its ranks.

Florida Congressman Randy Fine has become particularly notorious for his anti-Muslim rhetoric.

Cair indicated that Monday's attack on the Islamic Center of San Diego, California, is as "predictable as it is unacceptable".