The investigation will cover charges of murder, storing and using illegal weapons, and resisting law enforcement, Hanoi police said Friday.

30 protestors were arrested Thursday following the clash that occurred in Dong Tam Village, My Duc District, 40 km (25 miles) south of the capital city. 

Several people used grenades, petrol bombs and knives to attack police forces and disrupted public order, the Ministry of Public Security said in a website statement. Eight grenades, dozens of knives and 20 unused petrol bombs, among other weapons, were recovered at the scene.

As of Friday, the situation in Dong Tam Village has been "stabilized," said To An Xo, spokesman for the public security ministry.

Barricades have been erected on the provincial road 429, about 5 km away from Dong Tam Village. Stores on either side of the road have been closed. People wishing to enter or leave Dong Tam need to show identification papers.

Thursday’s clash happened a week after some units of the Ministry of National Defense, in collaboration with local authorities, began building a fence for the Mieu Mon Military Airport in Dong Tam Village, the Ministry of Public Security said.

The deadly clash was the latest incident in a long-standing dispute over the land. Protestors had said that they were not properly informed that the land was transferred to the military at some point. Officials however said the land belonged to the military.

Tension rose and came to a boil in February 2017, when military-owned telecom giant Viettel started work on building the airport. Upset villagers then took 38 police officers and government officials hostage in a communal house to protest work on the military airport. The standoff was resolved a week later, but in July 2017, local government inspectors announced that the land in Dong Tam Village in My Duc District has always belonged to the military.

While land disputes are not uncommon in Vietnam, it is the first time in decades that policemen and civilians have been killed in one.