Two British human rights campaigners have disappeared in Qatar while investigating the country's treatment of migrant workers.
Krishna Upadhyaya, 52, and Ghimire Gundev, 36, were last in contact on Sunday after sending panicked texts to colleagues claiming they were being followed by Qatari police.
Upadhyaya, who lives in Norway, and Gundev, from London, were working with Nepalese officials in the Qatari capital Doha to investigate the abuse of Nepalese workers.
Speaking to ITV News, the Norwegian charity employing the men said it had yet to receive any information from the Qatari authorities despite numerous requests.
"Global Network for Rights and Development (GNRD) is deeply concerned that these employees, both British citizens, may have been subjected to enforced disappearance and are currently at risk of torture," the charity said.
Their families have appealed for their immediate release.
The Foreign Office told ITV News it was aware of the reports and was investigating.
The two men checked out of their hotel on Tuesday but after becoming increasingly concerned about their safety, decided to remain in the hotel reception.
Mr Upadhyaya said he noticed "undercover authorities" becoming too close to him when he was speaking on the phone and expressed "alarm" at the number of police in the area.
It is believed both left the hotel but did not board their flight.
In the days before their disappearance, Mr Upadhyaya and a Nepalese official he was working with confronted someone who they thought was following them and urged them to stop.
In a later text message to colleagues in Norway, Mr Upadhyaya said: “I am being followed by the police here. Looks like they will be giving me trouble now!”
Mr Gundev's family, based in London, have urged the Qatari authorities to clarify the situation, describing the photographer as a "kind-hearted man".
Mr Upadhyaya is described as a "loving father-of-two" who has been campaigner for human rights for over two decades.
A Foreign Office spokesman said: "We are aware of reports of two British nationals missing in Qatar and looking into them."
The Qatari embassy in London could not be reached for comment.