DUBAI, United Arab Emirates — Two Britons researching migrant worker issues in Qatar, the Persian Gulf nation that is due to host the 2022 World Cup, disappeared after one of them reported being harassed by police, according to the Norwegian human-rights group that employs them.

The Global Network for Rights and Development said Thursday that researcher Krishna Upadhyaya, 52, and photographer Ghimire Gundev, 36, were supposed to leave Qatar via the capital Doha on Sunday. Their whereabouts are not known.

Fahad Atalla, project manager for the group in Norway, said he believes Qatari security services were behind the disappearance, but he could not give evidence to support the assertion.

According to the rights group, Upadhyaya contacted a friend in Norway on Saturday saying that Qatari police were following and harassing both men. He was working on a report on overworked migrant workers, according to a statement issued by his family.

An official at the British Embassy in Doha, speaking on condition of anonymity in line with government policy, said the mission is aware of reports that two British nationals have been detained by Qatari authorities and is investigating the matter.