Police have released a CCTV image of a man wanted over separate sexual assaults in London.
In the first incident, a man followed a woman in her 20s along Kilburn Park Road in north London at around 10.35pm on Monday, June 1.
He tried to engage the victim in conversation before touching her inappropriately, police said. She was then able to flee to the Queen's Head pub nearby and police were called.
In another incident, a man followed a woman as she walked home from work through Queen's Park.
She had taken the bus before getting off at the junction of Carlton Vale and Pentland Road, before walking through a park.
Police said the victim noticed the man but continued to walk through an alleyway, believed to be in Malvern Road, and then turned on to Saltram Crescent.
Again, the man attempted to engage her in conversation before touching her inappropriately and pressing himself against her.
The woman then ran off in the direction in which the pair had just walked and contacted police.
A Metropolitan Police spokesman said: "The suspect in both incidents is described as a black man, in his late teens to early 20s, 5ft 9ins to 6ft tall, of slim build with short black hair.
"In both incidents the suspect was wearing a grey hooded top with dark coloured jeans and white trainers. However, in the first incident he was also wearing a black jacket.
"The suspect is described as appearing immature and unsure of himself."
Detective Chief Inspector Jane Corrigan, added: "I am very concerned that these events could escalate into a serious sexual assault. I would urge anyone who recognises the man in the CCTV image to contact officers as a matter of urgency."
Anyone with information is asked to contact Westminster CID via 101 or Crimestoppers anonymously on 0800 555 111.
