NARATHIWAT, Thailand: Marines fending off a major militant assault on their base in Thailand’s violent south killed 16insurgents in an overnight shootout, authorities said Wednesday. It was 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-style uniforms attacked the marine corps base in Bacho district in Narathiwat province just after midnight Wednesday, said Capt. Somkiat Ponprayun, theprovincial marine corps special task force chief.

The shootout ended with 16 militants killed and the rest fleeing, Somkiat said. The death toll was reduced from the initial figure of 19 given out earlier Wednesday by regional army spokesman Col. Pramote Promin.

Somkiat said soldiers who fended off the attack suffered no casualties. He said the marines had been tipped off by the locals and warned of the assault.

Fighting in Thailand’s three southernmost provinces has occurred on a near daily basis since the insurgency flared anew in 2004, 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.

Muslims in the deep south, a Muslim-majority region in the Buddhist-dominated country that was once independent, have long complained of discrimination by the central government in 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.

The losses Wednesday were the most since guerrillas launched simultaneous attacks on police stations and checkpoints in the three provinces in April 2004, triggering clashes in which more than 100 militants were killed, 32 of them at the Kreu-Sae mosque in Pattani where they were holed up.

Cmdr. Thammanoon Wanna, who oversees the marine corps base, said the troops had braced for Wednesday’s assault after authorities discovered a sketch that mapped out the insurgents’ plans on a militant who was shot dead in recent days.

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 (3 miles) of the base for Wednesday night into Thursday.

“The insurgents were uplifted because of a surge in their successful attacks in recent weeks, so this is a significant loss on their side,” said Sunai Phasuk, a Bangkok-based researcher for Human Rights Watch. “From now, authorities will certainly have to be very concerned about their retaliation.”

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.

Officials from security agencies are scheduled to meet Friday to discuss safety measures for the southernmost provinces.