Police have arrested a 30-year-old man on suspicion of burglary after officers climbed a rooftop to detain him.
Onlookers in Northern Parade spotted a man on the roof of a house and called the police shortly after 10am.
A police spokesman said damage had been reported to the property.
A cordon was put in place on Gladys Avenue while officers dealt with the incident.
Pictures taken by an eyewitness show police approaching a hooded man on a rooftop in Northern Parade, before taking him down to the ground.
Police used a ladder to reach the rooftop.
The spokesman added that a 30-year-old man had been arrested by officers and is now in custody.
First Portsmouth tweeted that police had closed Twyford Avenue in both directions, and bus services were being diverted via Gladys Avenue.
An employee from R&L Tyres, in Twyford Avenue, said he had seen a man on a rooftop near the former Avenue pub.
The services 8 and 17 were being diverted but are now back to normal.
Stagecoach also tweeted to say services were being delayed by about 20 minutes through North End.