HAT YAI, Thailand — A homemade bomb planted in a road killed three police officers Friday in insurgency-plagued southern Thailand, officials said.

Pongsak Khaonuan, a police investigator in Yala province, said the bomb was detonated as the officers’ car passed over it, wrecking the vehicle and killing the three instantly. Another officer was taken to a hospital with injuries. Police said they believe Muslim separatist insurgents were behind the attack.

More than 6,000 people have been killed since the insurgency flared in 2004 in Thailand’s three southernmost provinces, the only ones with Muslim majorities in the predominantly Buddhist country. Roadside bombings and drive-by shootings are common tactics of the insurgents, while the government has blanketed the region with soldiers.

Several high-profile attacks have taken place in recent months as the government and representatives of some insurgent factions have held preliminary peace talks in neighboring Malaysia.

In September, a bomb derailed a train in the south, killing one person and injuring another, while another explosion several days later in front of a school claimed three lives, including a father and his student daughter.

Insurgents are also believed to have been behind a series of bombing and arson attacks in August on targets in seven provinces popular with tourists, killing four people and injuring dozens more.