There have been a “number of fatalities” in a “serious firearms incident” in Keyham, Plymouth, with “several” other casualties receiving treatment, police have said.

The incident is “not terror related” and the suspect involved is not “on the run”, Plymouth MP Johnny Mercer has said.

The number of victims has yet to be confirmed. The MP for Plymouth Sutton & Devonport, Luke Pollard, tweeted: “Update: awaiting confirmation of number of victims but this looks like a very grim day for our city and our community”.

The South Western ambulance service said it was called at just after 6pm on Thursday to an “ongoing incident” in Keyham.

It tweeted: “We responded to the incident with a significant number of resources, including hazardous area response teams (HART), multiple ambulances, air ambulances, multiple doctors and senior paramedics. We will provide an update here in due course.”

A number of police vehicles are on the scene and several roads have been closed, according to reports.

Pollard, the shadow environment secretary, had earlier tweeted: “Really worrying news coming out of Keyham in #plymouth. Please can everyone stay safe, stay indoors and follow police advice.

“I’ve spoken to some local residents and the police and the situation looks very serious indeed. Please avoid speculation and please do not share images of any victims. Please keep our community in your thoughts and prayers.”

Mercer, the Tory MP for Plymouth Moor View, earlier wrote on Twitter: “I am aware of a serious and tragic incident unfolding in Plymouth. Please obey all instructions from the police and do not post rumour or speculation on social media. “

The home secretary Priti Patel called the incident “shocking” and said her thoughts were with those affected. She tweeted: “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.”

Devon and Cornwall police have also been contacted for more information.

More to follow