An east London hospital trust has been hit by a ransomware cyber attack that could affect thousands of files.

Barts Health Trust, which runs four hospitals in east London, including Whipps Cross in Leytonstone, has sent a message to staff urging them not to open email attachments from unknown senders.

Viruses such as ransomware are normally delivered via emails which trick the recipient into opening attachments and releasing malware onto their system in a technique known as phishing.

The trust has not confirmed how much of their system has been affected by the attack or if patient data has been compromised, but said it continues to investigate.

A trust spokesman said: "We are urgently investigating this matter and have taken a number of drives offline as a precautionary measure.

"We have tried and tested contingency plans in place and are making every effort to ensure that patient care will not be affected."

According to the Health Service Journal, the trust's filing system between departments has been turned off as the investigation takes place.

The incident follows a similar attack on the Northern Lincolnshire and Goole Foundation Trust in October, when malware was used to encrypt files on the trust's system and demand a ransom in order to access them again.

The trust did not pay the ransom, but was forced to cancel patient appointments as its systems were shut down to remove the virus.