Hundreds of police lined the streets of a Beijing shopping district on Thursday after a rare protest over a woman's death in the Chinese capital, highlighting tensions between authorities and migrant workers.

More than 15 police vans holding dozens of officers were visible outside the Jingwen clothing market in the capital's south, after hours-long demonstrations on Wednesday which locals said saw hundreds take to the streets.

Staff at the mall and surrounding shops said the protests were fuelled by police mishandling of the alleged suicide of a 22-year-old migrant worker from the poverty-stricken eastern province of Anhui.

Online commentators claimed that she had been gang-raped and thrown from the building to her death, but police say she jumped from the building and their initial investigations ruled out sexual assault and murder.

Migrants have flocked to the capital for decades in search of higher incomes, but are denied the same access to health and housing services as Beijing residents and sometimes report discrimination from police.

Police on Thursday lined shop entrances around the Jingwen market, a maze of hundreds of tiny clothing stores, nearly all staffed by women who have moved to Beijing from poorer provinces.

Family members of the 22-year-old, surnamed Yuan, accused police of withholding evidence, workers who witnessed the protest said.

Images posted online showed hundreds of police, some armed, dispatched to disperse the protests on Wednesday. "There were hundreds of police of all kinds, even a helicopter," said a market worker who asked to remain anonymous.

"Basically the police mishandled the situation and made it worse," said a tea vendor who gave his name as Wang. "They arrested some of the protest leaders, which made people even more angry.

"I'm not sure if there was any corruption, but there's a lot of suspicion of the police," he added.

Staff at the market said rumours about the girls death had spread online for days before the protest.

"Everyone knows its difficult for migrant workers in Beijing, the police don't treat them the same as locals," said the owner of a dress shop, also requesting anonymity.

China sees tens of thousands of large and small-scale protests each year over a range of issues from unpaid wages to government-backed land grabs in the countryside, but large-scale demonstrations are rare in Beijing.

Analysts say that most protests are sparked by specific cases of perceived injustice. Rumours that police had beaten a migrant street vendor to death in 2011 sparked violent riots in the southern city of Zengcheng.

"Popular unhappiness... is fuelled more by power inequalities than by income gaps," Martin King Whyte, a sociologist at Harvard University who has surveyed Chinese social attitudes, wrote this week in Foreign Affairs magazine.

"When they try to follow established procedures to challenge official unfairness, most likely they will fail or even get into serious trouble. And that is why they take to the streets," he said.