MANILA:  Five people killed in a battle with Philippine security forces were policemen and soldiers, authorities said on Tuesday as they looked into claims the violence was part of an illegal gambling turf war.

The official police report following the shootings in a town about 170 kilometres (105 miles) south of Manila on Sunday said security forces tried to stop armed members of a criminal gang at a road block, setting off a battle.

Thirteen "gang members" were killed, according to the initial account.

However national police chief spokesman Generoso Cerbo said on Tuesday that Senior Superintendent Alfredo Consemino, a top policemen in a town near where the shootings occurred, and two of his aides were among those killed.

Armed forces spokesman Colonel Arnulfo Burgos also confirmed two of the others shot dead were an air force lieutenant and a sergeant.

Another of the 13 killed was Victorino Atienza, who operated a highly lucrative illegal gambling operation called "jueteng".

Media reports said that slain policeman Consemino was the gambling lord's business partner.

They also alleged that the police officer who led the team that manned the roadblock may have been working with a rival jueteng operator, and that the killings were part of a turf battle.

Cerbo, the national police spokesman, said those allegations would be investigated.

"The investigation will try to find out why these police personnel were in the company of an alleged gambling operator," Cerbo said, adding authorities would also probe claims the 13 were executed and not killed in a shootout.

"The official police report of our personnel on the ground said it was a shoot-out between the elements of a private armed group and the police and the military," Cerbo said.

"But with this allegation of a 'rub out' (slang for execution) we have decided to create a fact finding team to get to the bottom of this incident."

Jueteng is an illegal lottery known to generate millions of dollars that are often used to finance campaigns by corrupt local politicians.

Then president Joseph Estrada was forced from power in 2001 by mass street protested triggered by allegations he received millions of dollars in kickbacks from jueteng operators.

Corruption has long been a major problem in the Philippines, including in the police and armed forces.

President Benigno Aquino, who came to office in 2010, has said fighting graft through all sectors of society is his administration's top priority.