Britain's National Cyber Security Center says teams are working "round the clock" to restore hospital computer systems after a global cyberattack that hit dozens of countries forced British hospitals to cancel and delay treatment for patients.

The attack, which locked up computers and held users' files for ransom, was believed the biggest of its kind ever recorded. Several cybersecurity firms said they had identified the behind the attack, which has apparently hit Russia the hardest.

British Home Secretary Amber Rudd said Saturday that 45 were hit, but she stressed that no patient data had been stolen.

Germany's national railway says departure and arrival display screens at its stations were affected Friday night, but there was no impact on .