Fightback has begun against rioters: British PM

David Cameron says "nothing is off the table" in the new measures to take on the rioters.

LONDON: British Prime Minister David Cameron said Wednesday that a "fightback" was underway after four nights of rioting, adding that more robust policing had calmed the situation in London overnight.

Cameron said "nothing is off the table" in the new measures to take on the rioters, and he said security chiefs had decided to authorise the use of water cannon for the first time in mainland Britain, if they are required.

"We needed a fightback and a fightback is underway," Cameron told a news conference outside 10 Downing Street after the second meeting of Britain's COBRA security committee in as many days.

"While they are not currently needed, we now have in place contingency plans for water cannon to be available at 24 hours' notice," Cameron said after the riots spread from London to several other northern and central English cities.

British police were also already authorised to use "baton rounds" of plastic bullets, Cameron said.

The Conservative prime minister also revealed that police were in the process of arresting suspects based on CCTV images and he said "phoney human rights concerns" would not prevent police from detaining suspects.

"We will not allow a culture of fear to exist on our streets," Cameron said.

"It is all too clear that we have a big problem with gangs in our country. For too long there has been a lack of focus on the complete lack of respect shown by these groups of thugs."

Water cannon have been used to deal with sectarian violence in Northern Ireland, but have never been turned against crowds in mainland Britain.

Although an extra 10,000 police in London on Tuesday night helped prevent a repeat of three nights of violence in the capital, looting and rioting broke out in Manchester, Birmingham and other cities in the English Midlands.