At least fifteen people were killed in attacks by suspected Muslim militants in Thailand’s violence-racked south, an army spokesman said on Wednesday, the latest incident in the 15-year bloody insurgency.

Thailand’s three southernmost provinces have been in the grip of a conflict that has killed more than 7,000 people, as Malay Muslim militants fight for more autonomy from the Thai state.

The region is under martial law, heavily policed by the military and sometimes staffed with trained civilian volunteers, with residents and rights groups accusing them of heavy-handed tactics.

Late Tuesday militants struck two checkpoints in Yala province manned by civil defense volunteers, opening fire on them as a group of villagers stopped to talk, southern army spokesman Pramote Prom-in told AFP.

In the largest death toll in years, “12were killed at the scene, two more (died) at the hospital, and one died this morning,” said Pramote, adding that five others were injured.

The attackers took M-16 rifles and shotguns from the checkpoints, he said. “These acts were by militants.”

Nails were also scattered on the roads in an apparent effort to slow the security forces, the army said in a separate statement.

The areas surrounding the checkpoints have been closed off and are currently under forensic investigation.

Prime Minister Prayut Chan-ocha said the perpetrators must “be brought to justice,” according to Defense Ministry spokesman Kongcheep Tantravanich.

Rebels seeking autonomy for the culturally distinct region bordering Malaysia have been fighting the Buddhist-majority Thai state, which colonized the area over a century ago.

The conflict is characterized by tit-for-tat attacks that usually target symbols of the Thai state and its security forces but civilians from both Muslim and Buddhist communities often get caught in the crossfire.

The violence has bled into tourist destinations, like in 2012 when a series of car bomb in Songkhla province’s Hat Yai killed 13 people.

The incidents have been fewer in recent years, but the hits have been “more intense,” said Don Pathan, an expert on the so-called Deep South.

Tuesday’s attack marked the largest coordinated effort “in a very long time,” he added.

It comes days after Bangkok hosted the Association of Southeast Asian Nations (ASEAN) summit, which brought head of states from all over the world — along with hundreds of foreign press media, said Pathan.

“It (the attack) is a reminder that they are still here,” he said.

The rebels accuse the state of railroading their distinct culture as well as carrying out routine abuses which go unpunished.

The latest incident stoking outrage in the region was the death of Abdulloh Esormusor, a Muslim man who was detained by the military and left in a coma after being interrogated at a notorious Thai detention center.

Suspects are routinely taken for interrogation and held under emergency laws in detention centers where rights groups have documented torture.

Days after Abdulloh’s detention, four people were killed in a late-night attack on a military outpost, fueling speculation of a retaliatory operation.

A week later several small bombs exploded in Bangkok, injuring four people as the city hosted a major summit attended by top diplomats, including U.S. Secretary of State Mike Pompeo.

Thailand has linked the bombs to southern insurgents and said the devices used were similar to those found in the south — though no group ever claimed responsibility for the attacks.

KEYWORDS religion, military, Thailand, ethnicity, insurgencies