ScotRail has asked customers to consider alternatives to one of its Inverness to Edinburgh services because it has become so busy.

It said demand for its 10:51 Monday to Saturday train could be so high some passengers were unable to get on.

Discounts of up to 60% have been offered on two earlier services.

The alternative journeys take longer and involve changing at Perth or Stirling, but ScotRail said customers would arrive in Edinburgh earlier.

A single ticket to Edinburgh on the 10:51 can cost ?50 but the price can drop to about ?18 if passengers take one of the earlier trains.

The operator said it had been unable to add extra carriages to the 10:51 service to better cope with demand.

The state-owned company is publicising the situation on social media, and in a tweet says: "It pays not to get the 10:51".

The tweet features a video that says Inverness to Edinburgh services were popular with visitors due to the scenery the trains pass through, including locations such as the Drumochter Pass, Dalwhinnie and Blair Atholl.

But the video also warns the 10:51 service can get so many bookings it results in some people turning up to get on being unable to travel on the service.

A spokesman said: "It's not possible to add anymore carriages to the service, and this is the alternative being offered to customers.

"This is an attempt to alleviate the pressure on one service, and utilise the alternatives.