POLICE launched a major security operation after an alleged gunman threatened to shoot police officers just days after a terrorist attack in London.

Southend Police Station was locked down on Sunday as armed officers launched a frantic search for a man thought to be in possession of a firearm.

Helicopters were sent up to monitor traffic along the A127 while armed police scoured roads off Sutton Road, in Southend.

A major police presence was also visible in the Belfairs Park area and along the seafront, where the blue heavy-duty riot van was deployed.

A 26-year-old man was detained in Westcliff after an operation that lasted for more than 12 hours.

He was arrested on suspicion of making threats to kill and possession of a gun.

An Essex Police spokesman said: “A man has been arrested on suspicion of making threats to kill and possessing a firearm with intent to endanger life.

“Police were called to reports of a man making threats towards someone in an address in the Leigh area at around 5.45am on Sunday, August 27.

“Officers arrested a 26-year-old man in Westcliff on Sunday evening in connection with the incident and he remains in police custody.”

The man, from Southend, was still being questioned at the time of going to press.

Armed police were also placed on guard outside the police station in Victoria Avenue with nobody allowed in or out during part of the morning.

The spokesman added: “As part of the operation the police station was closed for a short period on Sunday. It is not believed there was an adverse impact on the service to the public.

“Threats were made against a number of individuals and a policing operation and appropriate safeguarding measures have been put in place.”

The spokesman said the incident was not linked to terrorism, but police are on heightened alert because the terror alert level is “severe” – meaning an attack is highly likely.

A Luton man was arrested on Friday night after allegedly driving at police officers outside Buckingham Palace and attacking them with a sword.

Police said the evacuation of Southend Pier because of a bomb scare was a coincidence.

Officers were called to the landmark at 10.45am on Sunday to reports of a suspicious object.

The coastguard later identified the object as a lump of concrete.