Hong Kong police yesterday rejected reports that the mother of a child spotted urinating in the street had slapped a local man who confronted her and her husband about it.

Police had received a report of a fight on Sai Yeung Choi Street in Mong Kok, Xinhua news agency reported yesterday, and they found four people involved — Hong Kong men surnamed Wang, 28, and Wu, 28, a 33-year-old mainland man surnamed Ye, and his 29-year-old wife Fu.

Wang was unhappy that the couple had allowed their 2-year-old son to urinate in the street and took pictures of the family with his smartphone, police said.

Ye grabbed Wang's phone to remove the memory card while Fu pushed a pram into Wu when he tried to intervene, they added.

Ye and Fu were taken away by police on suspicion of theft and assault.

Fu was released on bail and is due to report back to police in mid-May, while her husband was released unconditionally, police said.

It had been reported that Fu had slapped one of the two Hongkongers, but an investigation found no evidence of that, police said.

Video clips of Wang and Wu arguing with the couple caused a stir online over the weekend with thousands of comments posted.

Hong Kong media described the two men as heroes confronting ill-mannered mainland tourists.

On the mainland, opinion was divided, with some people saying the parents lacked basic decency while the majority said they had done nothing wrong. They had done all they could to find a public toilet and to prevent making a mess in the street by holding a diaper under the child.

Some said Hong Kong residents should be held partly responsible because no one had offered to help the couple find a toilet.

They said that although there were laws against urinating in the street in developed countries there was a tolerance and understanding for people who were old, weak, ill, disabled or pregnant.

In the UK, children are allowed to obey the call of nature in public, especially on grass areas or at the roadside.

In general though, public urination is illegal and subject to a fine although the UK's Law Commission has said that a police officer can make an exception for a pregnant woman.

In America, people can call the police when they see people urinating in public and fines of at least US$50 can be imposed.

In 2012, it was reported that a couple from Massachusetts allowed their 2-year-old son to urinate on a lawn in Philadelphia after a local clothing store refused to allow them to use its toilet.

Though they were fined US$50, mothers across America expressed support for the couple.