Several people were killed and wounded in shootings at two police headquarters in Vietnam’s Central Highlands on Sunday, authorities said.

Six people were arrested in connection with the shootings in Cu Kuin district of Dak Lak province, according to the ministry of public security’s website.

Investigators were searching for more suspects, it said.

The attacks on the police headquarters of both Ea Tieu and Ea Ktur communes occurred in the early hours of Sunday, according to the site.

It said a number of people, including police, local officials and civilians were killed and wounded but did not provide exact figures.

Police could not be reached immediately for comments.

The Central Highlands, home to a number of ethnic minorities, is considered a sensitive area for Vietnam’s authoritarian government and has long been a hotbed of discontent over issues that include land rights.

Some tribes in the area — collectively known as Montagnards — sided with the US-backed south during Vietnam’s decades-long war.