MANILA-- President Rodrigo Duterte on Friday refused to take sides over the killing of four soldiers in the hands of police officers in Jolo, Sulu, as he promised a full investigation into the incident.

Duterte urged the Armed Forces of the Philippines to wait for the findings of the National Bureau of Investigation over the incident.

"I am not ready to condemn anybody except that you should give time to the NBI to finish the [investigation]. They have started and they are at it now," he told an audience of soldiers in Zamboanga City.

"Help me make the waters calm," he added.

The President said he recognizes that the killing of the soldiers might have caused "animosity" between the Philippine National Police and the AFP.

"There is an investigation and I am giving you my word of honor that the investigation will proceed to find out the truth unfettered, unbridled by anybody," Duterte said.

The killing of the soldiers has stoked tensions between the military and police following conflicting claims on the incident.

Police alleged that the soldiers fled a checkpoint in Jolo on Monday and drew their guns at the officers, prompting them to fire.

But Philippine Army chief Lt. Gen. Gilbert Gapay denied this, calling the incident a "rubout."

Gapay said the soldiers cooperated and identified themselves as military personnel but they were still fired upon.

• Duterte: Expect fair investigation, truth to come out in soldiers’ killings in Sulu