Burkina Faso's military government says it has arrested eight members of a Dutch-based humanitarian organisation, accusing them of "spying and treason".

They are three Europeans, a Malian, and four Burkinabé - among them the NGO's country director and deputy. The organisation said they were detained some time ago but it was not previously reported.

Security Minister Mahamadou Sana said the NGO had "collected and passed on sensitive security information that could be detrimental to national security and the interests of Burkina Faso, to foreign powers".

The International NGO Safety Organisation (INSO), which provides safety information to aid workers, has "categorically" denied the allegations.

Anthony Neal, a representative of the NGO told the BBC's Newsday programme that its Burkina Faso country director had been detained since July when the organisation was suspended. The seven others were arrested later.

"We continue to work towards their safe and immediate release," he said.

The NGO was suspended on 31 July for three months by the authorities for "collecting sensitive data without authorisation". It has been working in the country since 2019.

On Tuesday, the security minister said that despite being banned, members of the organisation had continued to secretly collect information and hold meetings.

Mr Neal denied the claim, saying its information-collection activities had ceased on 31 July but its staff remained in Burkina Faso to deal with the detention and meet its contractual commitments.

A statement by the organisation emphasised that the information it collects was not confidential and was meant for the safety of humanitarian workers.

It added that the Burkinabé authorities were "fully aware" of their work and mandate and had been co-operating with the authorities.

Mr Neal said he had tried to engage with the government to address any misunderstandings or concerns. He said safety information was critical, with a "record" number of aid workers having been killed this year around the world.

Burkina Faso's military government led by Capt Ibrahim Traore seized power in a coup three years ago, and has had a frosty relationship with Western nations ever since.

In response to a worsening Islamist insurgency, the junta stopped working with the former colonial power, France, and instead turned to Russia for military assistance.

Human rights groups have since accused the army of committing abuses against civilians while tackling the militants, and also cracking down on political dissent and freedom of expression.