A teenager was dragged into a park in an attempted abduction the day after a girl was asked to get into a man's car.
The 13-year old was pulled into Archbishop Park in Lambeth by a man at about 08:00 GMT on Wednesday, but managed to escape when a passing dog walker shouted at him.
On Tuesday, an 11-year old was approached by a man in Streatham Hill around 07:50 GMT. She declined to get in his car and boarded a bus.
Detectives are appealing for witnesses.
They said they are keeping an open mind as to whether the two reports are linked.
The suspect in the first attempt was white, approximately 5ft 10ins tall with a medium build and short blond hair. He was wearing a black bomber-style jacket, blue jeans, and black lace up leather shoes described as "smart looking".
The second suspect was also white, approximately 35 to 40 years old. He was wearing black thick frame square glasses, a black baseball cap, black jacket and black trousers.
Det Insp Ian Kenward said: "These are two very worrying incidents and we appeal to anyone who was in or around the areas at the time they occurred to contact police.
"Any piece of information may prove valuable to the investigation."