Major London hospitals have been targeted by ransomware attacks by Russian hackers. The criminals hacked into the IT systems responsible for reporting on patient tests, the Independent reports.

Highly ranked sources in the hospitals describe the situation as a “catastrophe”. Staff are forced to write down patient test results on paper and manually transmit the results to emergency services.

Hospitals canceled or postponed non-urgent surgeries and procedures, and general practitioners were ordered to cancel all non-emergency blood tests.

Several senior National Health Service sources warned that it could take months to fully recover from the attack.