Trump's proposal for a "total and complete shutdown" of Muslims entering the US came after last week's deadly shooting in San Bernardino, California by a Muslim couple believed to have been radicalized by extremists.

But Muslim leaders across the US - including those viewed as US allies - warn that the Republican candidate's rhetoric could further radicalize disaffected individuals as well as provoke attacks.

"It is reckless and simply un-American. Donald Trump sounds more like a leader of a lynch mob than a great nation like ours," Council on American-Islamic Relations executive director Nihad Awad told a news conference in Washington, DC.

The comments dominated front pages in the US on Tuesday, including some particularly critical photo splashes.

Numbers from Pew Research Center in 2011 estimated there were 2.75 million Muslims in the US, although community leaders say the number is at least six million strong, likely higher.

Most US Muslims have arrived in the US in recent decades, making them a relatively fresh immigrant group. Many say they are watching the billionaire real estate mogul-turned-reality TV star-turned rising political star with alarm.

"He's giving the right to people to hurt us," said Egyptian-American travel agent Ahmed Shedeed who also runs The Islamic Center of Jersey City, New Jersey. "I'm asking him, I'm begging him. It has to stop - all these accusations. Look at the Muslim community as part of the American mosaic and we are part of America. We are not going anywhere."

Meanwhile, leaders in the Muslim-majority countries reacted with alarm the heated rhetoric coming from a candidate polling the strongest for the Republican nomination.

"This hostile vision towards Islam and Muslims will increase the tension within American society," Egypt's Dar Al-Iftaa said in a statement. "It is unfair to sanction all Muslims because of a group of extremists... we can't accuse one religion or one country of being a source of extremism and terrorism."

In the UK, the country's first Muslim to be appointed a Chief Crown Prosecutor, Nazir Afzal, said that Trump's proposal could end up restricting US efforts to combat Islamist violence.

In Australia, a country fraught with tensions over immigration, Keysar Trad, chairman of the Islamic Friendship Association of Australia, said Trump's statement reflected political desperation.

"Donald Trump's statement is a desperate statement by a desperate man who knows that he's clutching at straws and has no chance of winning the election. So he's trying to win it off the back of the Islamophobia industry."

Critics have pointed out that Trump's plan would be unconstitutional and almost certainly fail any court challenge. The candidate has not clarified whether his proposal would affect both tourists and immigrants, nor did he say whether it would target American Muslims currently abroad.

jar/msh (AFP, Reuters, AP)