First Bus have confirmed that their services will terminate in the city centre whilst the Wight Link has also been temporarily suspended.
The Gosport Ferry has also been suspended, as well as the Clarence Pier and Long Curtain Moat car park and footpaths, in Gosport.
Hampshire Constabulary has said there is a 300m cordon in place that has seen Tower Alley, Bath Square, West Street, the Camber and the Hotwalls area evacuated and cordoned off.
Bath Square, West Street, Broad Street and Tower Street have also been closed, as well as Gunwhaf Quays.Rest centres have been set up in St Thomas’ Cathedral for evacuated residents of Old Portsmouth and at the John Pounds Centre in Queen Street for Gunwharf Quays residents and Wight Link customers.
Alan Cufley, Portsmouth City Council’s director of transport, says the council is work with the police to ensure traffic continues to flow.
Cllr Cufley said: ‘Constant monitoring of the network and managing key junctions have allowed the traffic to continue to flow as normally as possible both in and out of the city.
‘Under the circumstances this has proven to be a very successful operation.’
Hampshire Police has urged members of the public to avoid these areas.
A spokesperson said: ‘We are supporting the Royal Navy to ensure the safe evacuation of the area as they prepare to tow the device out to sea.
‘We understand that this will cause disruption for some time however our priority is the safety of everyone in the area.’