Anti-Muslim campaigning feeds extremist propaganda: State Dept

Anti-Muslim rhetoric on the US campaign trail is "fodder" for extremist propaganda, the State Department warned Monday, after Donald Trump demanded a block on Muslim immigration.

The State Department spokesman was careful not to mention the Republican frontrunner by name, but cited Trump's appearance in a video made by Somali militants to bolster his case.

"The fact that one such candidate's comments were used in a recruiting video for an extremist group proves my point exactly," John Kirby told reporters at a daily briefing.

In footage that surfaced last week, the Somali al-Qaeda franchise Shebab used an excerpt of a speech Trump made in December after a radical couple in California killed 14 people.

In his speech, Trump proposed a "total and complete shutdown" on Muslims entering the United States until US authorities are "able to determine and understand this problem".

The Shebab video response argued that this showed the United States is about to turn on its Muslim minority and urged believers to flee the West to become fighters abroad. 

Trump has stood by his stance since the speech, repeating his call for a block on Muslim refugees and immigrants in interviews and in his first campaign television commercial.

The State Department spokesman, while insisting he did not want to be drawn into the campaign debate, noted that Secretary of State John Kerry has already warned about harmful rhetoric. 

"I won't talk about specific rhetoric by specific candidates," Kirby told reporters.

"But the secretary's been clear that there's not a religious test here in the United States - and nor should there be - when it comes to bringing in immigrants or refugees.

"Comments to the contrary can be perceived by those extremists themselves as fodder for why their narrative is correct, why people should join their group," Kirby continued. 

"Obviously it's a free country - people can say whatever they want - but they should be mindful of how those comments are perceived," he urged.

The first main hurdle of the US presidential campaign comes on 1 February, when candidates vying for the Republican and Democratic party nominations compete in the Iowa caucus.

Multi-billionaire property magnate and reality television star Trump is the Republican frontrunner in national polls, but faces a tough challenge from conservative senator Ted Cruz in the Iowa race.