UNITED NATIONS -- Indigenous people fighting to protect their rights must band together and build a global campaign to fend off unwelcome development and encroachment that forces them off their land, a UN expert has said.

A concerted effort could boost security and worldwide support for local communities locked in deadly struggles against governments and companies over land, said Vicky Tauli-Corpuz, UN Special Rapporteur on the Rights of Indigenous People.

Threats and violence against indigenous people over property rights are being fueled by right-wing governments, she said as indigenous leaders from around the world held talks in New York this week.

She singled out Brazil and the Philippines, her homeland which last year sought to have her declared a terrorist.

In Brazil, the administration of right-wing President Jair Bolsonaro is seeking to open its indigenous reserves to mining and commercial development.

"We have to launch a global campaign against criminalization and impunity against indigenous people," Tauli-Corpuz told the Thomson Reuters Foundation.

A concerted campaign with an online presence, databases and other tools could help activists share information and generate support globally, she said.

"What protects people is when it's a global issue, and people are coming to support us and denounce these things," she said. "You have to really talk of protection measures that are community-based."

Nearly four land and environmental activists were killed each week in 2017, according to the most recent tally by Global Witness, a British-based human rights organization.

Many are fighting the development interests of multinational corporations seeking to extract minerals, oil and gas.

Some of the activist leaders attending the meetings at the United Nations left to attend an annual rally in Brazil over indigenous rights.

Indigenous people live in Brazil on vast reservations that account for about 13 percent of the country's territory, long a source of conflict over their natural riches.

Globally, up to 2.5 billion people live on indigenous and community lands that make up more than half of all land worldwide, but they legally own just 10 percent, according to rights groups.

"This enables government to label communities illegal," Tauli-Corpuz said at a UN event late on Tuesday.

"The rapid surge of authoritarian political movements now threaten to reverse hard-won games and make matters worse."