Britain's health system has recovered from the disruption caused by a global cyber attack, with 97 percent of the country's health service trusts now "working as normal", interior minister Amber Rudd said on Saturday.

Speaking after chairing a meeting of the crisis response committee, or COBRA, Rudd said 48 of 248 health service trusts in England had been impacted by Friday's attack, but that all except six were now functioning normally.

"The response has in fact been very good," she said. "We think we have the right preparedness in place and also the right plans going forward over the next few days to ensure that we limit its impact going forward."

Earlier, Rudd said the government did not know who was behind the attack, which also hit some companies.