A fishing village of about 20,000 people in southern China is in open revolt against the local government a day after it announced the death in police custody of a villager who had led protests over an alleged land grab, according to residents.

Villagers say the man was murdered, but police say he died of a heart attack.

The villagers have forced local officials and police to flee Wukan in the southern province of Guangdong—China's export powerhouse—and have erected barricades to prevent them from re-entering, according to residents.

The police have responded by imposing a blockade on Wukan, stopping food and water from entering, and preventing local fishing boats from heading out to sea, the residents said.

Outside Wukan, life appeared normal with shops and markets open. Police erected a roadblock three or four miles from Wukan and checked cars traveling in both directions. They prevented a Wall Street Journal reporter from entering.