Police have detained nearly 20 people after a street crowd beat two urban security officers into comas, leaving one in critical condition in Lingxi township of Cangnan county in East China's Zhejiang Province.

One officer has regained consciousness, said a statement posted Sunday evening on the official website of the county government publicity department.

Five officers in total were thumped and kicked by the crowd after they or their comrades allegedly beat up a passerby themselves for trying to photograph them.

All five were taken to hospital. The injured resident was taken to the township's People's Hospital with minor injuries. He was stable after being transferred to another hospital for further observation, a county statement said on Friday.

All the injured officers were workers temporarily hired "to transport objects during the law enforcement process," town chief Wu Zhaopeng said in the statement.

The men were hired to move obstacles blocking the city sidewalk, the official explained.

A quarrel erupted on Friday morning when officers told a merchant to move his gas tanks off the sidewalk in line with city regulations, the Ningbo-based Modern Gold Express reported.

A passerby took a photo of their argument with his phone and when he refused to stop shooting, the officers beat him.

Online rumors that they beat the man to death went instantly viral, an official statement alleged on Friday.

Thousands of residents flocked to the street, the report said, surrounding all the chengguan officers' vehicles. One car failed to escape and its five passengers were removed and beaten by residents.

Police arrived at 4 pm and by 8 pm the crowd was dispersed and order was resumed, the report said.

The mass street brawl was just the latest in a series of conflicts between street law enforcers and residents in the last few years, highlighting simmering urban tensions.

Such conflicts are worrying, Yang Weidong, a professor at the Chinese Academy of Governance, told the Global Times, as they reflected another loss of credibility in law enforcement and local government.

"Sometimes even if the law enforcers carry out the duty without any flaw, there can be conflict," he said.

With mutual disbelief between government and people, rumors spread fast and worsen the situation, he said.

Many participants had nothing to do with the dispute, he opined, and were "simply venting their frustrations."

Calls to the county publicity office and the police by the Global Times went unanswered.