RIO DE JANEIRO: A Congolese park ranger, a Guatemalan indigenous land rights activist and an octogenarian Australian who blocked a coal mining firm from taking her family's farm were among the six winners of one of the world's most prestigious environmental prizes on Monday.

Announced in San Francisco, the 2017 Goldman Prize Environmental Prize worth $175,000 to each winner comes as violence against land rights campaigners continues to rise globally. Two previous winners of the prize were murdered for their activism.

In January, gunmen assassinated Mexican Isidro Baldenegro, one of the 2005 winners and anti-logging campaigner. Honduran indigenous rights advocate Berta Caceres, who won the prize in 2015, was shot dead last year.

"That environmentalists are under threat is a reflection of what's happening in the world right now," said Lorrae Rominger, acting director for the Goldman Prize Environmental Prize.

"Activists fighting very powerful interests are being targeted," Rominger told the Thomson Reuters Foundation in an email.

The prize committee is looking at ways to improve safety for the winners so they can continue their campaigns, she said.

Globally, more than three environmentalists and land rights activists were killed a week in 2015, up from two a week in 2014, according to the latest report by Global Witness, a U.K.-based campaign group.

Some of this year's prize winners say danger is part of life for environmental campaigners.

Rodrigue Katembo, 41, a ranger in the Democratic Republic of Congo's Virunga National Park, went undercover at significant personal risk to document corrupt practices by an oil company looking to drill in the protected area.

His expose about the firm's attempt to bribe officials led the oil company to withdraw from the project. But as part of the investigation, Katembo was arrested and tortured for 17 days, the Goldman Prize committee said in a statement.

INDIGENOUS LAND

Another winner, Rodrigo Tot, a land rights campaigner and community leader of Guatemala's indigenous Q'eqchi people, said one of his sons was murdered because of his activism.

"The fight to defend our land has been very hard. I lost one of my sons," Tot, 59, said in a phone interview.

Tot has led campaigns to protect indigenous land from government and foreign mining companies seeking to tap into the nickel deposits in central Guatemala.

He says nickel mines would have poisoned local water sources by discharging untreated wastewater in streams and lakes used for fishing and farming.

"Our land has a lot of natural resources and sources of water. We don't want our resources to be polluted," Tot said.

His campaigning led to a rare victory when Guatemala's Constitutional Court ordered the government in a landmark ruling in 2011 to issue land titles to the community of around 400 people living in the village of Agua Caliente.

But the fight continues. So far, the government has failed to comply with the court's ruling.

"We still don't have our collective land rights. We are always looking for ways to put pressure on the government," Tot said.

Australian family farmer Wendy Bowman, a co-winner of the prize, is known for her successful fight to stop coal mining expansion that she says causes air and water pollution.

Bowman, 83, is one of the last residents left in Camberwell, a small village in Hunter Valley in southeastern Australia, an area surrounded by coal mining.

She stopped Yancoal, a Chinese-owned mining company, from taking her family farm and has refused to sell her land to the company, the prize committee said.

Other winners include Uros Macerl, an organic farmer from Slovenia who successfully blocked a cement facility which activists say would have produced toxic waste, Indian anti-mining campaigner Prafulla Samantara and a Los Angeles community organizer who goes by the name Mark! Lopez.