There have been a "number of fatalities" and "several" other casualties are receiving treatment following a "serious firearms incident" in Plymouth, Devon and Cornwall police say.

A shooter involved in the incident has been shot and is believed to be dead, Sky News' Mark White has been told.

It is not being treated as terror-related and the incident, in Biddick Drive, in the Keyham area of the city, has been contained, police added.

A critical incident had been declared and the area cordoned off.

Devon and Cornwall Police said: "Police were called to a serious firearms incident in Biddick Drive, in the Keyham area of Plymouth at around 6.10pm today.

"Officers and ambulance staff attended. There have been a number of fatalities at the scene and several other casualties are receiving treatment.

"A critical incident has been declared. The area has been cordoned off and police believe the situation is contained."

Home secretary Priti Patel tweeted: "The incident in Plymouth is shocking and my thoughts are with those affected.

"I have spoken to the Chief Constable and offered my full support.

"I urge everyone to remain calm, follow police advice and allow our emergency services to get on with their jobs."

She was echoed by Shadow home secretary Nick Thomas-Symonds who posted: "Truly terrible news. Thinking of the families and friends of those who have died and those injured. Thank you to our remarkable emergency services."

Plymouth Sutton and Devonport MP Luke Pollard said it was "a very grim day for our city and our community".

The Labour frontbencher added that he was "awaiting confirmation" of the number of victims.

Plymouth Moor View MP Johnny Mercer also said on Twitter that the incident is "not terror related", adding that the suspect involved is "not on the run".

Image: Police said the incident in the Keyham area has been contained. Pic @dylan_hainey/Twitter

In an earlier tweet he said: "Please obey all instructions from the police and do not post rumour or speculation on social media."

Meanwhile, Plymouth Argyle FC tweeted: "Our hearts go out to victims of tonight's tragic incident in our city, alongside their families, friends, and the wider Plymouth community."

South Western Ambulance Service said "Hazardous Area Response Teams (HART), multiple ambulances, air ambulances, multiple doctors and senior paramedics" were all sent to the scene of of the incident at 6.12pm.

Multiple police vehicles remain in the area.