A section 35 dispersal order was put in place by Hampshire Constabulary on Sunday evening, in a bid to tackle anti-social behaviour along the coastline over the bank holiday weekend.
The order was made as part of Operation Nautical, which includes increased patrols in hotspots over the summer.
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Posting on Facebook, Portsmouth police said: ‘Southsea is a superb place to enjoy the open spaces, the seaside, the restaurants bars, local amenities and leisure facilities.
‘Please ensure that you enjoy these areas and that respect is shown to the many others wishing to do so.
‘Anti-social behaviour will not be tolerated and individuals or groups will be directed to leave the area should they fall foul of acceptable behaviours.’
Not obeying the order after being banned from the area is a criminal offence.
A similar dispersal order was enforced in April this year, after anti-social gatherings in Old Portsmouth.
Operation Nautical follows a summer of chaos on Southsea Common last year that saw a woman violently attacked and police forced to disperse large crowds.
The operation also follows the riot in Old Portsmouth in 2019 when more than 100 youngsters ran amok.
Parks across the city and Southsea Common are included in the operation’s scope.
Hampshire’s marine unit and the Ministry of Defence Police, whose numbers have swelled in the city since the carriers have made the city their homeport, will also be involved.