Groups of hooded and masked youth moved throughout London and other cities Tuesday as police and citizens girded themselves for another night of violence. Witnesses reported gangs barricaded themselves and threw rocks at passing motorists. Parts of London were virtual lock-down with massive looting, attacks on journalists and fires started in residences, businesses and government facilities, British media reported. Prime Minister David Cameron, cutting short his vacation because of the riots, vowed to restore order and called Parliament back into session Thursday in response to the \"sickening scenes.\" The unrest began Saturday after a peaceful protest in London\'s Tottenham neighborhood over the fatal shooting of a man by police. A resident of London\'s Ealing area was said to be \"in critical condition after facing rioters,\" The Daily Telegraph reported. Scotland Yard said a 26-year-old man found shot in a car in Croydon during rioting in the south London town died at a hospital. France, Austria and Italy issued travel advisories warning their citizens to use caution when visiting Britain, especially if they\'re going to city centers at night. China questioned whether London could provide adequate protection during next year\'s Summer Olympics, a comment dismissed by British officials, the Telegraph said. The London Metropolitan Police deployed 16,000 police officers and canceled leave to deal with the widespread violence engulfing London. Police leaders also have been discussing whether to use plastic bullets as a response if necessary. Police in Manchester warned people to stay away from the city\'s downtown area because of the unrest. The police said a Wigan man was arrested on suspicion of using social media to incite disorder. Officials in Birmingham, Liverpool, Nottingham and Bristol also reported violence, including police vehicles being burned, stores looted, buildings set ablaze, violent confrontations and scores of arrests. The Telegraph reported residents have begun forming human chains to defend their homes. \"People were still looking on and taking pictures but we weren\'t letting anyone in a mask or hood through,\" Clapham Junction resident John Comyn said. \"Whenever people tried, people in the line rounded on them and they would turn back. This happened fairly regularly, in fairly small groups.\" Labor Party leader Ed Miliband, who spent the afternoon touring areas of destruction in Peckham, said there was \"no excuse for the violence and intimidation of people ... . That can never be excused, that can never be justified.\" Restoring order was the immediate priority, Miliband said. \"We can\'t allow some areas of London to be essentially no go areas where people feel frightened to go on the streets,\" he said. Cameron told rioters they would feel \"the full force of the law. And if you are old enough to commit these crimes, you are old enough to face the punishment.\" Recalling Parliament would allow lawmakers to \"stand together in condemnation of these crimes and to stand together in determination to rebuild these communities,\" he said. London Mayor Boris Johnson cut short his vacation to return to the city, as did Home Secretary Theresa May, the BBC said. \"These have been the worst scenes of violence and disturbance on our streets for many, many years, and this sort of violence, this level of criminality, this thuggery, this looting, this theft, is completely unacceptable,\" May told the BBC. \"We can deal with it. We can deal with it with robust policing, with good use of intelligence, but also with the help and support of local communities.\"