Security personnel investigate around bodies of insurgents at the site of an attack on an army base in the troubled southern province of Narathiwat on Tuesday. — Reuters PATTANI, Thailand — Marines fending off a major militant assault on their base in Thailand's violent south killed 19 insurgents in an overnight shootout, authorities said Wednesday. It was believed to be the deadliest toll the Muslim guerrillas suffered since more than 100 died in a single day nearly a decade ago. About 50 militants wearing military-like uniforms raided the marine corps base in Bacho district in Narathiwat province late Tuesday night, Col. Pramote Promin said. The shootout ended with at least 19 militants killed and the rest fleeing, Pramote said, adding that soldiers who fended off the attack suffered no casualties. He said the marines had been tipped-off by the locals and were alerted for the assault. Regional army commander Lt. Gen. Udomchai Thammasaroraj said in an interview on ThaiPBS channel that the army has declared a curfew for the area within 5 kilometers of the base for Wednesday night into Thursday. An insurgency erupted in 2004 in Thailand's three southernmost provinces, a Muslim-majority region in the Buddhist-dominated country. In April of that year, guerrillas launched simultaneous attacks on police stations and checkpoints in the three provinces, triggering clashes in which more than 100 militants died; 32 of them were killed at the Kreu-Sae mosque in Pattani where they were holed up. Sunai Phasuk, a Bangkok-based researcher for Human Rights Watch, said the overnight toll was the worst since then. “The insurgents were uplifted because of a surge in their successful attacks in recent weeks, so this is a significant loss on their side.” Sunai said. “From now, authorities will certainly have to be very concerned about their retaliation.” He said Narathiwat province has been a contested area between security forces and militants. Muslims in the south have long complained of discrimination by the central government in the capital, Bangkok, and the insurgents are thought to be fighting for autonomy. But the insurgency itself remains murky, with militants making no public pronouncements on their goals. Fighting in the area is reported on a near daily basis, and more than 5,000 people have been killed. Security forces, as well as teachers, have been targeted by insurgents because they are seen as representatives of the government. On Sunday, suspected militants killed five soldiers and wounded five others in two attacks that included a car bomb blast in Yala province that was detonated as a truck carrying six soldiers passed. The militants then opened fire on the soldiers, killing five of them, and took away the dead soldiers' rifles, he said. Officials from security agencies are scheduled to meet Friday to discuss safety measures for the southernmost provinces. — AP