British spies believe North Korea was behind the NHS cyber attack last month.

The WannaCry ransomware attack affected more than 60 NHS trusts as well as Fedex, Renault and Telefonica.

Those targeted by the hack were asked to pay money to have their data restored.

British cyber experts examining the hack believe it was created by a North Korean cyber gang called the Lazarus Group.

British spies believe North Korea was behind the NHS cyber attack last month

British security sources are unsure whether the attack was ordered by the North Korean government.

An investigation by America's National Security Agency (NSA) said it had 'moderate confidence' the attack pointed to North Korea's spy agency, the Reconnaissance General Bureau, the Washington Post reported.

The NSA believes it was an attempt to raise money for the cash-strapped despotic state.

The assessment follows the findings by security company Symantec, which said it was put together by the Lazarus hacker group working on behalf of the regime.

The Washington Post said the evidence gathered in the report was 'not conclusive' but strongly suggested North Korea's involvement.

This graphic shows how ransomware can quickly infect an entire computer system

As a money-making scheme the hack seemingly failed as, so far, none of the $140,000 (£110,000) in bitcoins raised in ransom payments by victims has been withdrawn.

Security experts believed this is because the transactions will be easy to trace, meaning they will be able to find the creators.

North Korea has repeatedly denied involvement in cyber attacks against other countries.

Intelligence company Flashpoint said its analysis suggested hackers fluent in Chinese were responsible.

In addition, James Scott, a senior fellow at the Institute for Critical Infrastructure Technology, has thrown doubt on links between Lazarus and Pyongyang.