Wales weather: Icy snap sees ambulance calls exceed capacity
Demand on the Welsh Ambulance Service has "exceeded its capacity to respond" to calls, with some people being asked to make their own way to hospital.
"Extreme weather, coupled with a high call volume focused on falls and breathing issues overnight, has limited our capacity to respond safely and timely," said director Lee Brooks.
A Met Office warning for ice and fog is in force across parts of Wales.
Meanwhile, police said icy conditions had caused a number of accidents.
The Welsh Ambulance Service has declared a "business continuity incident" after receiving more than 2,000 emergency 999 calls on Saturday, a 17% increase on last week.
It said the NHS 111 Wales helpline had also received more than 10,000 calls, "the busiest day ever for the service", with icy roads affecting its ability to respond promptly to callouts.
The service has urged people to only call 999 in a life-threatening emergency such as a cardiac arrest, chest pain or breathing difficulties, loss of consciousness, choking, or catastrophic bleeding.
It also said the 111 helpline continued to be busy with calls for advice about children "very high" due to parents being cautious about possible strep A symptoms following a number of cases.
It said it had put arrangements in place to "manage demand, including asking some patients to make an alternative arrangement, such as making their own way to hospital".
South Wales Police has said there were several collisions along the M4 because of the weather.
Highways service Traffic Wales tweeted that snow had fallen across the country, causing poor conditions.
Rhondda Cynon Taf council said conditions were bad on the A470, and advised drivers to only travel if they had to, while an accident on the A449 in Raglan, Monmouthshire, left the road partially blocked.
The A4233 at Trebanog in Tonyrefail, Rhondda Cynon Taf, was closed in both directions. The road was described as impassable, and there was also a two-vehicle accident on Trebanog Road.
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South Wales Police tweeted: "Road conditions across the south Wales area are extremely poor.
"There are several reports of black ice, including the M4, and some roads have been affected by snowfall.
"Only drive if it's necessary. Please allow extra time for your journey."
The latest snow came after the weather warning was extended from Saturday into Sunday.
On Sunday afternoon the Met Office issued a new warning of ice and fog from 16:00 to 11:00 on Monday for Flintshire, Wrexham and Powys.
Saturday saw road closures in several places due to snow and ice, including in Denbighshire, Ceredigion, Powys, and Wrexham.
People have been warned to expect icy patches on some untreated roads, pavements and cycle paths, with a risk of injuries from slips and falls.