Transport minister Humza Yousaf has met rail commuters in Glasgow following a breakdown which brought trains in the central belt to a standstill.

ScotRail called the incident in Edinburgh on Thursday morning the "worst type of train failure in the worst part of our network at the worst possible time".

The broken down train had to be split into two parts to be moved after its brakes locked near Princes Street Gardens at 7am, causing delays across the network.

ScotRail has been heavily criticised for its handling of the incident and is carrying out an internal review.

Speaking at Glasgow's Queen Street Station on Thursday morning, Mr Yousaf said: "The key message is to apologise to commuters for the disruption that took place yesterday.

"We expect ScotRail to improve their performance and I'll be monitoring that closely."

Mr Yousaf warned ScotRail could lose its contract if it does not make improvements.

Train drivers' union Aslef has urged the First Minister to replace Mr Yousaf and return ScotRail to public ownership.

General secretary Mick Whelan said: "The Scottish Government response to the rail crisis has been pathetic.

"Transport minister Humza Yousaf has stood by while Abellio ScotRail takes Scotland's passengers and taxpayers for a ride."

He added: "Nicola Sturgeon must take personal responsibility for this situation as her government awarded this contract.

"She should sack her incompetent transport minister. You can't control what you don't own so the Scottish government should do the decent thing and return the railway to public ownership."

Nicola Sturgeon apologised for the incident at First Minister's Questions on Thursday.

But Scottish Labour leader Kezia Dugdale called it "yet another shambolic day on our railways".

Ms Dugdale said that performance figures for ScotRail on Wednesday were 79% compared to a target of 91%, meaning more than one in five trains failed to arrive on time, while for rural areas this was 60%.

MSPs heard the long-term figure is around 89%.