The Chinese government has been worried about university student restiveness with the economic slowdown shrinking job opportunities, especially ahead of the June 4 anniversary of the crackdown on student-led demonstrations in Beijing in 1989.

Students from the Nanjing University of Aeronautics and Astronautics on Monday confronted city management officers who they said tried to clear away a female student running a curbside stall near the university, said the Hong Kong-based Information Center for Human Rights and Democracy, adding that 30 students were injured and a police vehicle was trashed.

Chinese internet sites circulated accounts and pictures that they said showed the confrontation, which appeared to draw hundreds of young people, most of them onlookers.

The protest in Nanjing, a city with many universities, appeared to be a passing symptom of the economic crisis.

Some young people held signs declaring, "Non-violent non-cooperation," one account (www.campus-business.cn) said.

"University students have a hard time finding work...and have been running stalls," said that account, which also said the city management officials tried to confiscate the student's goods.

City management officials are a law-and-order force used to keep streets clear and fine illegal traders. They have been the target of complaints in many parts of China, where locals claim they are often brutal and abuse their powers.

But an officer at a police station near the university denied there had been a clash, and an official at the university also said he knew nothing of it.

"I do not know about this," said an officer in the local Jiangning police station. She gave only her surname, Shi.

Some Chinese blogs also disputed that people were injured or that university students were involved. There were no accounts in official media, which has become increasingly candid about small protests. (Reporting by Chris Buckley and Beijing Newsroom; Editing by Nick Macfie)