Umno politicians have criticised Australian senator Fraser Anning over his remarks regarding the fatal attacks at two mosques in Christchurch.

Venting his anger on Twitter, Khairy Jamaluddin did not mince words in calling him a “piece of s**t”.

“The real cause of bloodshed on New Zealand streets today is the twisted minds of racist, despicable pieces of s**t like you,” said the Rembau lawmaker.

Anning's remarks had also infuriated Umno secretary-general Annuar Musa.

“It is sad and disheartening to see the attacks and murder... It is sadder when a politician like Anning makes a statement which is insolent towards Islam. We feel challenged,” he tweeted.

“Your understanding of Islam is simply horrible and terrifying. Your remarks are simply. You owe an apology to Muslims throughout the world,” he said.

In a statement issued after the incident which left 50 people dead, Anning, among others, said the real cause of the bloodshed is the immigration problem which allowed “Muslim fanatics” to migrate to New Zealand.

He added that while Muslims were the victims in this incident, they are “usually the perpetrators”.

New Zealand Prime Minister Jacinda Ardern has condemned the attacks as an act of terrorism.

The suspect shooter, who is in his late 20s, has been arrested and will appear at the Christchurch court on Saturday.