Britain said it was investigating Thursday after two British researchers were reported detained in Qatar while probing the working conditions of migrants building infrastructure for the 2022 football World Cup.
"We are aware of reports that two British nationals have been detained in Qatar and we are investigating," a spokesperson for the British embassy in Doha told AFP.
The Norway-based Global Network for Rights and Development (GNRD) said Wednesday that two British staffers -- Krishna Upadhyaya and Ghimire Gundev -- had disappeared in the Qatari capital after complaining of being followed by police.
They had been carrying out follow-up research on the working conditions of migrant labourers after Qatari authorities promised a raft of reforms to address an international outcry over working conditions as the emirate prepares to host football's premier tournament.
Upadhyaya had sent a text message to managers complaining that they were "being harassed and followed by Qatari police," the rights group said.
It demanded "immediate cooperation from Qatari authorities to fully disclose the whereabouts and current situation" of its researcher and photographer.
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"In the event that its employees are subjected to any kind of physical or psychological harm, GNRD is prepared to take all necessary legal action," it warned.
Rights watchdog Amnesty International spoke of the pair's "enforced disappearance," saying they went missing after checking our of their hotel in Doha on Sunday.
Their disappearance "is extremely worrying and the pattern of events reported by the men before they went missing indicates that they may have been detained in relation to their human rights work," said Amnesty's Said Boumedouha.
"The Qatari authorities must urgently reveal the fate and whereabouts of these two men and dispel the growing fears that they are at risk of torture or other ill-treatment."
Amnesty said it has written to the government to seek information about them.
Earlier this year, Qatar gave undertakings to improve workplace safety, housing and pay and conditions for its huge expatriate workforce after world football governing body FIFA came under huge pressure from rights groups to review its decision to award the emirate the 2022 World Cup.