The robber brandishing a kitchen knife rushed into Dolly's Newsagents in Fairfax Drive, Westcliff, at 9.17pm on Friday before threatening an employee.
But two customers managed to get out of the shop unseen and flagged down a passing police car.
As two police officers entered the shop the robber ran towards then brandishing the knife and attempted to stab one of the officers.
Both officers aimed CS spray at the robber’s face which was mostly covered with a black ski mask. The man fled towards Prittlewell Brook near to the junction with Westbourne Grove.
A widespread search of the area was carried out by numerous police units and the Essex Police helicopter but there was no sign of the suspect.
Full story in Monday's Echo.