Brazilian police are questioning a man over the disappearance of a veteran British journalist who went missing in a remote part of the Amazon rainforest.
International pressure is ramping up for Brazilian authorities to act after Dom Phillips and Bruno Araujo Pereir, an Indigenous affairs official, vanished in the Javari Valley region more than three days ago.
A vigil is taking place outside the Brazilian Embassy in Central London for the two with protesters carrying large pictures of the missing men as they urge Brazilian authorities to ramp up the search operation immediately.
This comes as a 41-year-old suspect was arrested for allegedly carrying a firearm without a permit, a common practice in the region.
Police did not clarify why he was being treated as a suspect but he is thought have been among a group of men who threatened the pair near an indigenous territory on Saturday.
Mr Phillips, 57, a regular contributor to the Guardian, has reported from Brazil for more than a decade and had been working on a book about preservation of the Amazon.
He had photographed the men following the confrontation after they travelled by river to the territory's borders, according to the Univaja association of people in the Vale do Javari indigenous territory.
The association's president, Paulo Marubo, previously said the group had brandished firearms at a Univaja patrol.
Four other people have been questioned since the investigation started but no arrests related to the disappearances have yet been made, according to authorities.
The two men had been due to arrive by boat to nearby Atalaia do Norte on Sunday morning, but never reached the city.
Indigenous leaders on the ground, family members and peers of Mr Pereira and Mr Phillips have urged for increased efforts to find them.
The vigil, which has been promoted by Greenpeace, comes amid reported concerns that there had been little support from the authorities in the search.
Mr Phillips' wife, Alessandra Sampaio, recorded a video pleading with the government to intensify the operation.
"We still have some hope of finding them.
"Even if I don't find the love of my life alive, they must be found," she said in the video posted on Twitter.
Mr Pereira has long operated in Javari Valley for the Brazilian indigenous affairs agency as an advocate of the indigenous tribes and had received a number of threats from illegal fisherman and poachers.
On Tuesday, President Jair Bolsonaro was criticised for describing the two men's work as an "adventure".
"Really, just two people in a boat in a completely wild region like that is not a recommended adventure.
"Anything could happen.
"It could be an accident, it could be that they have been killed," he said in an interview with television network SBT.
"We hope and ask God that they're found soon.
"The armed forces are working hard."
