Qatar has confirmed it is holding two Britons who went missing while researching migrant labour issues, saying the men are being questioned for alleged illegal activity in the Gulf nation.

The Norway-based Global Network for Rights and Development said its researcher Krishna Upadhyaya, 52, and photographer Ghimire Gundev, 36, went missing on 31 August as they were preparing to leave Qatar.

It suggested that Qatari security services were behind their disappearance and has called for their release. Amnesty International last week urged Qatari authorities to reveal the men's whereabouts and ensure their safety.

Qatar's foreign ministry said on Saturday, in its first comment on the case, that the men were arrested and "being interrogated for having violated the provisions of the laws of the state of Qatar," according to a statement carried by the official Qatar News Agency.

The statement said that all actions taken against the men are "consistent with the principles of human rights" outlined in the laws of Qatar, and that British embassy officials have visited them to check on their situation.

An official at the British embassy in Doha confirmed on Sunday that the mission is providing consular assistance to the men but was unable to provide further details.

The GNRD is based in Stavanger in the county of Rogaland, and describes itself as a neutral organisation set up in 2008 to promote human rights and development. Many of its recent statements have focused on the conflict in Gaza and other issues related to the Middle East.

It has singled out Qatar in the past over conditions faced by migrant workers. Like many of its Arab neighbours, Qatar relies on vast numbers of mainly Asian low-paid migrant workers.

Its treatment of them has come under greater scrutiny since it won the right to host the 2022 World Cup, with labour rights activists raising concerns about dangerous working conditions, allegations of unpaid salaries and other abuses.

Egypt's official State Information Service noted in December that the GNRD supported listing the Muslim Brotherhood as a terrorist organisation, and the group has since described a constitutional referendum and May elections that led to the presidency of former military strongman General Abdel Fatah al-Sisi as a "democratic transition".

Sissi led the military overthrow of the Brotherhood-backed government of Mohammed Morsi last year. Qatar is a strong supporter of the Brotherhood and other Islamist groups – a position that has put it at odds with Gulf neighbors such as Saudi Arabia and the United Arab Emirates.