LONDON (AP) _ Police today arrested a dozen people suspected of belonging to a gang that committed a series of robberies, rapes and murders in south London and the neighboring Surrey and Kent countryside.

Police involved in the dawn raids resulting in the arrests said the suspected gang members apparently committed violence for thrills or because they were high on drugs.

Armed officers from the Surrey police and Scotland Yard joined forces to raid two south London addresses and arrested one woman and 11 men, police said.

Those arrested were taken to Croydon, 10 miles south of London, where they were being questioned.

Detective Chief Supt. Vincent McFadden, head of Surrey Criminal Investigation Department, said information about the possible identities of the gang members was given by known criminals sickened by the crimes.

''Attacking women and people in their own homes is abhorrent to them and they are willing to give us information, albeit anonymously, but information nevertheless,'' the police chief said.

Detectives link the gang with 11 unsolved crimes and believe they may have been responsible for many more.

On Dec. 5, three men from the gang raped a young mother in front of her baby son. On Thursday, gang members beat one man to death and a few hours later repeatedly stabbed another.

In the latest rampage Thursday night the gang, armed with a gun and machete, hijacked a car and fatally beat its driver, Peter Hurburgh, 57. His bound body was left in a field.

Early Friday, they broke into the home of retired businessman Richard Napier and ransacked the house, slashing and stabbing his son Timothy, 41, who was critically ill in a hospital today.