Armed Police have been called to a flat on Belgrave Place in the city this evening.
A large cordon has been put in place at Belgrave Place with the junction of Madeira Drive.
Officers were called just 11pm on Thursday evening.
Response officers and armed Police and a dog unit have both been seen at the location one resident has revealed that they have entered a property within the block after officers asked them to let them in and advised to say on their property.
It is understood to be drug gun related said a shocked bystander.
Officers controlling the cordon are advising people to keep back and for other resident to remain in their property whilst they deal with the incident
A spokesman for Sussex Police said: Officers were called to St George’s Road in the city shortly before 9pm this evening to reports of a male in possession of a firearm.
“Enquiries led police to Belgrave Place where firearms were deployed.
“A man has been arrested on suspicion of possession of a firearm and remains in custody.”