Police have linked two thefts in the city, both of which happened yesterday.
The first was at 3.57pm, when a 22-year-old woman was holding her mobile phone while standing outside her workplace at Konecta 32, Eldergate.
She was approached by a man on his bike who, as he rode past, snatched the phone from her hand. He then rode of in the direction of the Loughton over bridge.
The man is white, late twenties, with an average height, of a slim build with brown hair. He was wearing a Burberry check scarf over the bottom part of his face, dark blue waterproof jacket and tracksuit bottoms.
The second offence was around 4.10pm. A 27-year-old-woman was sitting on The Green, Loughton, using her laptop which was on her knee, when she was approached from behind by two men on bikes.
One of them reached down and took her laptop. Both offenders then rode off towards the park.
On both occasions the men were riding dark coloured mountain bikes.
Any potential witnesses can call police on 101 or Crimestoppers, anonymously, on 0800 555 111.