Officers were injured and vehicles were damaged during an anti-migrant protest in Portsmouth, police said.
Demonstrators clashed with police after hundreds gathered following the arrival of a small boat carrying migrants on Sunday.
They blocked roads for hours and vowed to stay all night in the second major anti-migrant protest in two days.
The government condemned the "thuggish" behaviour at the protest, with Sky correspondent Barnaby Papadopoulos reporting from the scene that demonstrators threw objects at police.
Police have now launched an investigation to identify those who committed offences at the protest.
Around 200 demonstrators who had gathered were dispersed at about 4am on Monday, according to Hampshire and Isle of Wight Constabulary.
The force said: "A number of police, Coastguard and Border Force vehicles were damaged during the evening.
"A small number of officers were treated at the scene for injuries, but no-one in attendance from any agency or the public was seriously injured.
"Violence and criminal damage have no part in peaceful protest.
"No arrests have been made at this time, however an investigation to identify offenders responsible for any assaults to officers, criminal damage to vehicles, or other criminal offences has been launched."
A dinghy, reported to be carrying some 140 migrants, was intercepted in the English Channel on Sunday.
It left the Jobourg region of Normandy in France and is thought to have made one of the longest journeys of any small boat - landings as far west as Hampshire are rare.
It was met in the Channel by two RNLI boats who took the migrants to Portsmouth.
Bystanders have now started taking life jackets away from Eastney harbour, where the boat arrived on Sunday.
A large pile of orange vests were left near the gangway to the shore.
Portsmouth council leader Steve Pitt said the Home Office has "serious questions to answer" after an "unsuitable" location was chosen to disembark the RNLI boats carrying the migrants.
Sunday's disorder followed protests in Dover on Saturday, when hundreds of masked, black-clad men blocked road access to the port.
In a statement, Kent Police said Saturday's demonstration involved some 200 people and caused "significant traffic disruption for several hours".
The force added there was no need for peaceful protesters to wear face coverings and an investigation for criminal damage to a road has been launched.
Assistant Chief Constable Nigel Brookes said: "There has been some discussion about the fact that protestors on Saturday wore face coverings.
"To do so is not, in itself, sufficient to establish a criminal offence.
"There is no need to wear a face covering in Kent, if your plan is to peacefully express your views."
(c) Sky News 2026: Officers injured and vehicles damaged during anti-migrant protest in Portsmouth - as p

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