Rural residents protesting against land grabs have clashed with police in north and south-west China, according to accounts posted online, in the latest cases to be sparked by one of the country's most potent sources of unrest.

Villagers in south-western Yunnan province were arrested and injured when police broke up a a three-day blockade of a highway over the suicide of a rubber farmer who complained her land had been illegally seized, according to an account posted by an unknown user.

An officer at the Xishuangbanna police station confirmed that officers had dispersed farmers whose protest had blocked the road for several days last week, but said he did not know if there had been arrests and denied that anyone had been beaten.

The local government could not be reached on Tuesday, a public holiday in China.

Land grabs are the primary source of rural unrest in China. This year the international land rights organisation Landesa, which surveys Chinese farmers annually, warned: "The pace of land takings continues to accelerate, often leaving farmers poorly compensated and embittered."

According to the online account, the rubber farmer, Li Xuelan, killed herself on 24 March over the land grab. The following day her relatives and colleagues held a memorial in the road, resulting in tailbacks more than three miles long.

The account said numbers swelled into the thousands. Two days later, about 300 riot and special police forcibly dispersed the protesters, injuring and arresting several people, it said.

Photographs posted with the account showed large numbers of police and villagers, with one showing an officer carrying a woman away.

Separately, an overseas rights group said police had detained 22 ethnic Mongolians after hundreds of them protested against the seizure of land in the northern region of Inner Mongolia.

Although the area has generally been seen as peaceful, last year saw the biggest wave of unrest for two decades after the death of a herder who had tried to stop a convoy of coal trucks.

There has been growing tension over damage to grazing land. More than 80 police used "brutal force" on Monday to break up a demonstration of Mongolians from Tulee village near Tongliao city, the New York-based Southern Mongolian Human Rights Information Centre said.

In a statement emailed to Reuters it said five protesters were seriously injured after trying to block a bulldozer from a state-backed forestry company from working on their farmland.

"Police violently beat up the protesters with batons. Some were bleeding, some were beaten down on the ground. Women were pulled by their hair and thrown into police vehicles," the group said, citing a protester.

They were reportedly seeking the return of about 4,000 hectares (10,000 acres) of land which they said the forestry company had stopped managing.

Police in the region said they were unaware of any protest, and a man who answered the phone at the Tongliao public security bureau said offices were closed.