Rioters fought with firefighters and police in the Canadian city of London, Ontario, as St Patrick’s Day parties spiralled out of control overnight.
Dozens of police were drafted in to deal with the unrest, which was sparked when several student parties spilled on to the streets.
Rioters hurled bottles at police and set a TV truck alight, feeding the flames with a propane tank and TV sets.
Police said 11 people were arrested and appealed for rioters to come forward.
Police were called out late on Saturday, but did not move in until 04:00 on Sunday (08:00 GMT).