The industrial action prompted warnings from healthcare leaders about straining a health system already in crisis.
Ambulance workers in the UK went on strike on Wednesday, widening a dispute with the government over its refusal to increase pay above inflation.
The walkout by National Health Service staff prompted healthcare administrators to issue warnings against straining a health system already in crisis and saw the government and unions furiously trade blame over the possible loss of life.
It comes after thousands of nurses in England, Wales and Northern Ireland took to picket lines on Tuesday, just five days after their first strike in their union's 106-year history.
Industrial action is paralysing Britain in the run-up to Christmas, with railway workers and passport control officers also threatening to strike over the festive period.
Trade unions have threatened further action in the new year if the government refuses to discuss pay.
But Rishi Sunak's Conservative government insists it must stick to modest increases for public sector workers as recommended by independent pay review bodies.
"The best way to help them and help everyone else in the country is for us to get a grip and reduce inflation as quickly as possible," the UK leader said.
Ministers have drafted in 750 military personnel to drive ambulances and perform logistics roles to mitigate the impact of Wednesday's ambulance strike, which has affected almost all areas of England and Wales.
Despite the government's insistence that it will not negotiate, polls indicate most people support nurses - and to a lesser extent other workers - walking out.