The first incident happened in Arcany Road, South Ockendon, on Monday, 6 May. A 16-year-old boy was threatened with a knife and had his mobile phone stolen.
On the same day, a 32-year-old man was assaulted in Arterial Road, Grays. The offenders attempted to steal his bag but failed.
Two days later, a 17-year-old boy had his phone stolen at knifepoint in Garron Lane, South Ockendon.
Officers from Essex Police attempted to stop a stolen Ford Fusion in Easington Way, South Ockendon, shortly after on Thursday, 9 May.
But the driver did not stop for officers.
The car, which had been reported stolen, was pursued and eventually stopped in Hubert Road, Rainham, where four people got out and ran off.
Three boys were arrested and officers are work to locate the fourth person.
A 17-year-old boy from Hornchurch was arrested on suspicion of robbery, attempted theft of a vehicle, theft from a vehicle, failing to stop, and dangerous driving.
Two 17-year-old boys from Rainham and Upminster were arrested on suspicion of robbery, theft from a vehicle, failing to stop, and dangerous driving.
All three have been released on bail until next month while enquiries continue.
Tags: Grays, Rainham, Hornchurch, Upminster, South Ockendon
