MANILA -- (UPDATED) The Philippine National Police (PNP) is looking into politics as the possible motive in the fatal ambush on Vice Mayor Alexander Lubigan of Trece Martires, Cavite.

Calabarzon police director Chief Supt. Edward Carranza confirmed this to ABS-CBN News on Sunday, saying Lubigan was set to run for a "higher position" in the 2019 mid-term elections.

Carranza declined to elaborate, saying instead that a special investigation task force has been formed to solve the vice mayor's killing.

Lubigan was in a sports utility vehicle when gunmen in another SUV opened fire on Saturday. His bodyguard was also killed in the attack that occurred outside a hospital in Trece Martires in broad daylight.

• CAUGHT ON CAM: Fatal ambush on Cavite vice mayor

The vice mayor, who was serving his third term, was not on the government's drug watch list, said Cavite police chief Senior Supt. William Segun.

Lubigan was the third local government official killed in a week.

Tanuan, Batangas Mayor Antonio Halili, who was linked by President Rodrigo Duteerte to the narcotics trade, was gunned down during a flag-raising ceremony last Monday.

Mayor Ferdinand Bote of General Tinio, Nueva Ecija was shot dead inside his vehicle a day after.

PNP chief Director General Oscar Albayalde promised to solve the killings, which he said have "disturbed and saddened" the police force.

"We likewise appeal for any information which may help us quickly solve these cases so that justice will be served to the victims and their families," he added in a statement.

With a report from Bianca Dava, ABS-CBN News