Two of the US Democrats' biggest, most left-leaning stars have been quick to hail New Zealand Prime Minister Jacinda Ardern's announcement today of an immediate ban on assault weapons in the wake of the terror attack on two Christchurch mosques last Friday.

Bernie Sanders. Source: 1 NEWS

Ms Ardern announced this afternoon that the Government is banning sales of military style semi-automatic rifles and high-capacity magazines like the weapons used in the mosque attacks that killed 50 people and injured another 50.

US Senator and presidential candidate Bernie Sanders tweeted after the announcement from Wellington, saying, "This is what real action to stop gun violence looks like.

"We must follow New Zealand's lead, take on the NRA and ban the sale and distribution of assault weapons in the United States," Mr Sanders wrote.

National Rifle Association spokesperson Dana Loesch reacted with a tweet defending the right of Americans to own guns.

"The US isn't NZ. While they [New Zealanders] do not have an inalienable right to bear arms and to self defense, we do."

New York Democratic representative Alexandria Ocasio-Cortez also praised Ms Ardern for the ban.

Ms Ocasio-Cortez referenced the Sandy Hook Elementary School shooting of December 2012 in Newtown, Connecticut, when 20-year-old Adam Lanza fatally shot 20 children and six adult staff members.

"Sandy Hook happened 6 years ago and we can't even get the Senate to hold a vote on universal background checks," Ms Ocasio-Cortez wrote.

"Christchurch happened, and within days New Zealand acted to get weapons of war out of the consumer market.

"This is what leadership looks like," she wrote, linking to news coverage of Ms Ardern's announcement.

The New Zealand Government is asking all owners of assault weapons or now-banned attachments to report them to the government in the next two days before turning them in.

Ms Ardern says the cabinet is also working on a gun buyback program to be announced later.