British police have arrested three men in London after suspected acid attack on a three-year-old boy in the English city of Worcester.

The boy was taken to hospital with serious burns to his arm and face after an incident at the Home Bargains store in Worcester, central England, on Saturday.

"He has since been discharged but the long-term implications of his injuries are unknown at this time," West Mercia police said.

Police said they had arrested three men, aged 22, 25 and 26, arrested on suspicion of conspiracy to commit grievous bodily harm. Another 39-year-old man remains in custody.

Britain has seen a steep rise in acid attacks recently and the government is taking action to tighten sales of corrosive substances, particularly to those aged under 18.