Emergency services have been called to a major train derailment near Stonehaven in Aberdeenshire, where smoke can be seen billowing from the track amid reports of an engine fire and serious injuries.

About 30 emergency vehicles, including an air ambulance, are reported to be at the scene already, with more continuing to arrive.

British Transport Police confirmed they were responding to the incident, stating: “Officers were called to the scene at 9.43am and remain there alongside paramedics and the fire brigade.”

Describing the incident as “extremely serious”, Scotland’s first minister, Nicola Sturgeon, confirmed before first minister’s questions in the Holyrood chamber that there were early reports of serious injuries, and that a major incident had been declared. She added that her thoughts were with all those involved.

The UK transport secretary, Grant Shapps, said he had been briefed on the incident by Network Rail, tweeting: “British Transport Police and Network Rail are on location, along with rail workers who were nearby. The UK government will provide every support. My thoughts are with those involved and their families.”

Some witness reports on social media suggested the train had fallen down an embankment after running into a landslip.

North-east Scotland was one of the areas badly affected by torrential rain and thunderstorms overnight, with flooding causing travel disruption and continued school closures on Wednesday morning.

The River Carron burst its banks and was pictured flowing through Stonehaven’s town centre.

Mick Lynch, the assistant general secretary of the Rail, Maritime and Transport union, said: “RMT is aware of the major incident at Stonehaven and our reps are liaising directly at senior level with both ScotRail and Network Rail.

“Our priority at this time is to support our members, their colleagues and their families and to do all that we can to assist the rescue operation which RMT members are currently involved in.

“The facts behind this incident will need to be established in due course but at this stage we are focused on support and assistance and our thoughts are with all those impacted by this tragedy.”