A 3-year-old boy was doused with acid or another corrosive substance while in a stroller outside a store in western England on Saturday, police say.

His arms and face were seriously burned, and there could be long-term implications for his health.

Officials say the child was targeted but have not publicly identified a motive.

A 39-year-old man was arrested on Sunday, and three men in their 20s were arrested on Monday.

The rate of acid attacks in the UK has been rising, and the government has introduced legislation to fight the problem.

Four men have been arrested after a 3-year-old boy was seriously injured in an apparent acid attack in western England.

The boy was deliberately targeted when a corrosive substance was thrown in his face on Saturday afternoon, West Mercia Police said. Officials have not said whether it was acid specifically or a different corrosive liquid.

The boy was taken to a hospital and treated for serious burns on his arms and face. He has been discharged, but police acknowledged the attack could still have "long-term implications" for his health.

The attack took place outside Home Bargains, a discount homewares store in Worcester, around 2:15 p.m. on Saturday. The boy was in his stroller at the time, police said.

A 39-year-old man was arrested on Sunday on suspicion of conspiracy to cause grievous bodily harm. Three more men, aged 22, 25, and 26, were arrested on suspicion of the same charge early Monday. None has been named.

Investigators have not publicly identified a motive for the attack.

The number of acid attacks in the UK has been rising over the past few years, and Britain has one of the highest rates of attacks with corrosive substances, including acid.

Some attacks have been related to gang fights, and London is facing the problem of moped riders using acid.

Unlike with knives, carrying corrosive substances was not a specific offense in the UK until recently, meaning it was harder for police to act against people who armed themselves in this way.

Legislation introduced in June would make it a criminal offense to sell a corrosive product to someone under 18 or possess a corrosive substance in a public place.