Residents said riot police had opened fire on Tuesday on protesters in the village of Dongzhou in Guangdong province after they moved in to quell the unrest.
Estimates from residents and rights groups put the number of dead between two and 20. Police sealed the village on Friday.
One villager said: "Now the authorities are coming to the village to detain people."
He added that his brother was among those shot dead during the demonstrations.
"My parents and my sister-in-law are kneeling in front of the house to ask the government officials to explain the killing," he said.
He put the number of dead at more than 10 and said bodies were lying in the villagers' houses.
Rule of law
China's Communist Party has a monopoly on power and brooks no dissent but protests are becoming increasingly common, sparked by disputes over land rights, corruption and a growing gap between rich and poor.
The Dongzhou dispute has centred on compensation for land taken to build a wind farm in the area, which lies on the east coast of the province along the South China Sea.
Residents said compensation allocated by the government was appropriated by officials.
A government official in the administrative centre of Shanwei said armed police had been sent into the area but that the violence was started by the villagers, who attacked police with pipe bombs.
"This is a society ruled by law. How can we let this kind of thing happen?"
A government official
"This is a society ruled by law. How can we let this kind of thing happen?" said the official, who gave his surname as Cai.
Residents said there were thousands of armed police in the area, blocking roads and detaining those suspected of involvement in the protests.
Another villager said: "A lot of families have moved away from the village. We are all very scared. At night, nobody dares go out."
US broadcaster Radio Free Asia said armed police had sealed roads into the area and that people were not allowed to enter or leave.