Australia’s leaders on Monday condemned anti-immigration protests over the weekend that saw tens of thousands of people gather in cities across the country, chanting slogans like “send them back” and “stop the invasion.”

The government has described the protests as racist and politicians from both sides of the aisle expressed concerns about the presence of neo-Nazi groups.

Australia is grappling with the growing threat of extremist ideology, amid a rise of far-right nationalism in countries around the world. Australia prides itself on its multiculturalism, but experts say discontent among some groups has been growing because of a lack of affordable housing and soaring living costs.

About 15,000 people gathered for the “March for Australia” anti-immigration rally in Sydney on Sunday, while as many as 3,000 people attended a counterprotest organized by a pro-Palestinian group, the police said. In other parts of Australia, the police said that thousands people attended rallies, but did not distinguish between protesters and counterprotesters.

Populist politicians made speeches at some rallies, while at others, members of neo-Nazi groups spoke and led chants of “heil Australia,” local media reported. Some clashed with counterprotesters. The police said they made a handful of arrests across the country.

Pauline Hanson, the leader of the far-right anti-immigration One Nation Party, spoke at the protest in Canberra, the nation’s capital.