Thousands of passengers are enduring major disruption after London King's Cross and Paddington were closed due to overrunning engineering works.

No trains are running in or out of either station, with passengers advised to defer their journeys to Sunday or Monday.

The King's Cross closure means East Coast and Thameslink & Great Northern passengers must start or end their journey at Finsbury Park in north London.

However National Rail said it was forced to temporarily close the station "due to overcrowding".

East Coast Trains had said it expected "significant disruption to services" due to delayed Network Rail works north of King's Cross.

And on Saturday morning First Great Western added to passengers' woes by confirming Paddington had been closed until at least 1.30pm.

"Over-running rail works have closed all lines in/out of London Paddington. Significant disruptions and delays likely to all such journeys," the company wrote.

The disruption comes as thousands of people are likely to be travelling following the Christmas break.

A reduced service to and from King's Cross will go ahead as planned on Sunday, with trains leaving up to 20 minutes earlier than normal.

East Coast spokesman Paul Emberley said: "Network Rail has apologised to passengers for the inevitable delays to their travel plans on Saturday as a result of the overrunning engineering works.

"East Coast is particularly sorry too for the inconvenience to its customers as a result, on what we know is an already very busy travel day immediately following the Christmas break.

"For customers intending to start or finish their journey at King's Cross, consideration should be given to deferring travel plans to either Sunday or Monday.

"We're working hard over the holiday period to make the necessary adjustments to our timetable as a consequence, and to provide as much information as we can."

The company added that tickets for Saturday will be valid on Sunday and Monday.

East Coast destinations include Peterborough, Leeds, Newcastle, Glasgow and Aberdeen.

Network Rail said the engineering work is part of a £200m (€255m) Christmas investment programme.

The work is among 300 projects being undertaken over the holiday period at 2,000 locations across Britain.

A Network Rail spokesman said: "What has happened is really regrettable and unfortunate, but it is a small part of a massive amount of engineering investment taking place over Christmas."