Philippine President Rodrigo Duterte threatened to end peace talks with communist rebels on Wednesday, hours after suspected guerrillas wounded four of his military bodyguards in an ambush.

Aides said Duterte, 72, was not in the convoy when gunmen opened fire on two Presidential Security Group vehicles along a highway on the main southern island of Mindanao, where martial law is in effect.

The government blamed the New People's Army -- the 4,000-member armed wing of the Communist Party of the Philippines -- and threatened to shelve peace negotiations unless the guerrillas stopped targeting soldiers in the south.

"The president directed the government panel... not to resume formal peace talks unless the reds (leftist rebels) agree to stop their attacks against government troops in Mindanao," said a statement issued by the presidential palace.

The latest communist attack came as government forces on Mindanao fought Islamic State group-inspired militants who have been holed up in the southern city of Marawi since May 23.

The communist party, which is waging Asia's longest-running insurgency, called on its armed wing on Tuesday to launch offensives in response to Duterte's plan to put Mindanao under martial law until the end of the year.

A 60-day martial rule is now in force on Mindanao as part of the military campaign in Marawi, but the Duterte government said Tuesday it needed more time to accomplish the mission.

The communist insurgency that began in 1968 and which the military says is now mostly waged in Mindanao has claimed an estimated 30,000 lives.

The rebels have been in off-and-on peace talks with the government since Duterte, a self-described socialist, was elected last year.

Both sides declared unilateral ceasefires, but these did not last.

Duterte suspended formal peace talks in May after both sides failed to resolve a dispute over a rebel order for fighters to step up attacks.

To try and end the two-month impasse, Duterte was planning to send negotiators shortly to an unspecified venue and informally discuss a possible bilateral ceasefire agreement, the government statement said.

But it warned that for formal peace talks to resume, the rebels must commit to "suspending operations against the military and the police and stopping all their extortion activities on the ground".

A senior Mindanao military official, Brigadier-General Gilberto Gapay, said the communists were behind the attack on the Duterte bodyguards.

"This is part of their nationwide call for armed groups to oppose martial law by launching intensified offensives against government forces," Gapay told radio station DZBB in Manila.

Source: AFP