A young mum was caught stealing nappies. This police officer stepped in.

A young mother caught shoplifting nappies for her baby was saved by the kind act of a police officer.

Officer Johns, from the Laurel Police Department in the US state of Maryland, was called to a grocery store in late July after reports a woman was caught shoplifting by security.

When he arrived, he learned the young mother had attempted to steal two packets of nappies for her infant son. She had purchased her groceries, but did not have enough money left to buy the nappies.

“Though we often joke that our field trainees are still in diapers, it turns out that rookie Officer Johns was not buying these for himself,” the police department wrote in a Facebook post that has now gone viral.

"Officer Johns considered the situation and then made the decision to purchase the diapers out of his own pocket so that the young child would not suffer.

"Though it's but a snapshot of some of the work your officers are doing daily, we still wanted to take a moment to thank Officer Johns for not just fairly enforcing the law, but also showing empathy to an innocent child put in a difficult situation."

The police department also noted the woman was still issued a criminal citation for the theft, something that was unavoidable if the store's policy was to press charges against all shoplifters.

The post - and image of Officer Johns purchasing the items for the young mother - has since been shared over 5,400 times, with many offering messages of support and donations to the young mum.

Others were willing to reimburse the officer for his kind act.

"I couldn't imagine what was going through her mind knowing that she couldn't afford to put diapers on her baby and had to steal them," one resident wrote.

"I hope I never have to feel that."

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"Please let us know if there's a way we can help this little one with diapers in the future or if the family can be connected... to get diapers when the baby needs them if the family can't afford to do so," another woman wrote.

"This police officer deserves to be recognised for going over and above the call of duty," said another.

Due to the overwhelming request to make donations, the police department has had to clarify that they are unable to release the woman's information due to confidentiality laws.

Instead, they are directing all donation requests to a service that offers a variety of help options, including short-term financial assistance, rental assistance, and help submitting applications for food stamps, to residents of the town.