Hundreds of drivers stranded overnight in freezing temperatures are still battling to get home as police launched a huge operation to free up miles of gridlock.

Some motorists were stuck in their vehicles for more than 15 hours as Scotland bore the brunt of a fresh wave of ice and snow which left several major routes impassable.

Police across the country's busy central belt warned people not to travel unless it was "absolutely essential" after temperatures plunged as low as minus 17C (1.4F) and hampered gritting efforts.

The deluge on Monday - which appeared to take the authorities by surprise - saw people sleep in their cars or abandon them on the highway as motorways and A-roads clogged up.

Around 100 children were also forced to sleep at their school after the bad weather prevented pupils, parents and staff from getting home.

North-east Scotland and north-west England are facing more snow, with widespread icy roads expected up and down the country thanks to the freezing conditions.

At least nine people have so far died in the big freeze, with an elderly man found dead in snow at a Lincolnshire caravan park the latest victim.

Temperatures plummeted to minus 13C (8.6F) in Edinburgh and minus 11C (12.2F) in Glasgow overnight, reaching minus 16.7C (1.9F) in parts of the Highlands. Parts of Yorkshire and South Wales also saw minus 14C (6.8F).

Glasgow and Edinburgh Airports were open after closing on Monday due to the weather conditions, but officials warned travellers to check with their airlines.

Belfast International and London City Airports also warned of delays and cancellations due to fog and freezing weather.

On the railways, the East Coast line between London and Edinburgh was still running a reduced service, and some Northern Rail services in Yorkshire and North Lincolnshire were cancelled.

Brendan Jones, a forecaster with MeteoGroup, the weather division of the Press Association, said temperatures were due to rise from Thursday through the weekend thanks to a shift in the wind direction: "At the moment, temperatures are struggling to get above freezing, but by Thursday most places are going to be above zero - 4C (39.2F) or 5C (41F) across large parts of the country. Many places will have a frost-free night."