Police are urging the public not to take the law into their own hands in Birkenhead.

The call came as a social media message circulates threatening vigilante-style action to prevent a repeat of last night's riot.

The message - sent on the controversial Blackberry smartphone network - asks local males to gather to "fight fire with fire."

Messages on the service, along with posts on Twitter, are believed to have helped plan the riot and are being blamed for bringing the gang of teenagers together to attack the town centre.

There are difficulties intercepting the instant messages sent via BlackBerry Messenger, known as BBM, to private networks of one or more people.

Unlike social networks such as Facebook and Twitter, it is possible to transmit messages through BBM that cannot be traced back to the sender.

A Merseyside Police spokeswoman said: "We would strongly advise people not to respond to this message or become involved."

She said police are appealing to the community for help in finding the rioters - and witnesses are asked to email any information or images they may have of the violence to the investigation team.

People are also asked to email any links to any footage they may have captured to disorderinvestigation@merseyside.police.uk Anyone with any information is asked to call Merseyside Police on 0151 709 6010, or Crimestoppers, anonymously, on 0800 555 111.

The force can also be contacted on Twitter @merseypolice