The journalist was travelling with a Brazilian indigenous expert in Brazil when they went missing.
A British journalist and a Brazilian indigenous expert have gone missing in a remote area of the Amazon rainforest.
Dom Phillips, a regular contributor to the Guardian newspaper in Brazil, was last seen in the Javari region, Amazonas state at the weekend.
He was travelling the area with Bruno Pereira while researching a book. The two had received threats days before, say indigenous groups.
Federal police and navy are searching for the two in the remote region.
Mr Phillips, 57, has written extensively on the Amazon and has lived in Brazil for over a decade.
Mr Pereira, who is currently on leave from his post with the government’s indigenous affairs agency Funai, is an expert on isolated tribes in the Amazon.
The two had been in the district for about a week and had travelled by boat to Jaburu lake on Friday.
They were then expected to return to Atalaia do Norte city on Sunday afternoon, according to the Union of Indigenous Organizations of the Javari Valley (UNIVAJA) and the Observatory for the Human Rights of Isolated and Recently Contacted Indigenous Peoples (OPI). But the pair never arrived.
According to UNIVAJA, the men had received threats in the days before their disappearance, but no more detail was given as to the nature of the threats.
The men’s families have expressed their alarm since the two went missing.
“We implore the Brazilian authorities to send the national guard, federal police and all the powers at their disposal to find our cherished Dom,” Mr Phillips’s sister’s partner, Paul Sherwood, wrote on Twitter.
“He loves Brazil and has committed his career to coverage of the Amazon rainforest. We understand that time is of the essence.”
Former Brazilian President Luiz Inacio Lula da Silva tweeted: “Phillips interviewed me for the Guardian in 2017. I hope they are fine, safe and will be found quickly.”
O indigenista Bruno Araújo Pereira e o jornalista inglês Dom Phillips estão desaparecidos na Amazônia. Estavam na região reportando invasões de terras indígenas. Phillips me entrevistou para o @guardian em 2017. Espero que sejam encontrados logo, que estejam bem e em segurança. pic.twitter.com/nuyJfmyOqr— Lula (@LulaOficial)
The Guardian said it was “very concerned” about Mr Phillips and was “urgently seeking information about Mr Phillips’ whereabouts and condition.”
The north-western Javari region – home to over 20 indigenous groups – has been hit by violence in recent years with a rise in illegal mining, fishing and hunting.
The government’s indigenous affairs agency, Funai, which has a base in the region, has also been attacked several times there in recent years.