Police are maintaining a cordon in a Southsea street.
Access to Edmund Road has been cordoned off between Fawcett Road and Francis Avenue for around eight hours.
The cordon was in place at around 9.30pm last night.
Uniformed officers and plainclothes police were in the area, along with a Boarhunt recovery vehicle.
It's not clear what the incident is but police are directing traffic from the area.
Policee seized a vehicle in Wheatstone Road.
The cordon remains in place as of 5.30am today.
Uniformed police officers are still guarding the scene.
Resident Gary Jones, 55, said he was told there had been a scuffle.
He said: 'There were all armed police up there.'