The ministry confirmed "a small number" of emails had been erroneously forwarded, with The Times reporting they had been intended for the US Department of Defense but were instead sent to Mali.

The mistake occurred because officials sent the messages to an address ending with the west African country's .ml domain, rather than the US military's similar .mil address, according to the newspaper.

The majority of messages contained trivial information, such as holiday staffing schedules for officials, but others had detailed descriptions of British research into hypersonic missiles, the paper noted.

The revelations come after the Financial Times reported last week that millions of US military emails had been misdirected to Mali because of typos.

"We have opened an investigation after a small number of emails were mistakenly forwarded to an incorrect email domain," the UK Ministry of Defence said in a statement.

"We are confident they did not contain any information that could compromise operational security or technical data.

"All sensitive information is shared on systems designed to minimise the risk of misdirection."

The ministry added it "constantly reviews its processes and is currently undertaking a programme of work to improve information management, data loss prevention, and the control of sensitive information".

Mali is one of several allies of Russia in Africa, with the Russian paramilitary group Wagner operating there.

Its paramilitaries protect the current regime, conduct military operations and training and advise on the revision of mining laws and even of the constitution.

The United States this week sanctioned Mali's defence minister and two officials it accused of facilitating Wagner's activities there, which Washington said acts "as a proxy military force of the Kremlin".