Motorcycle-borne gunmen on Tuesday assassinated a mayor in a town north of the Philippine capital, the second such killing of an official in two days, police said.

Ferdinand Bote, 57, became the 12th elected local official murdered since Rodrigo Duterte, the Philippine president, unleashed a deadly anti-narcotics campaign after coming to power two years ago, although Mr Bote was not linked to the drug trade.

He and his driver were leaving a government office in the capital of Nueva Ecija province when gunmen approached his sport utility vehicle and shot him dead, said Adrian Gabriel, the town's police chief.

"He was repeatedly shot with the use of a short firearm," police said in an initial report, but the driver escaped unhurt. Police retrieved at least 18 empty shells at the scene.

The government will spare no effort in getting to the bottom of the latest crime, said Harry Roque, a spokesman for Mr Duterte.

"We assure everyone that we will discharge the state obligation for every murder," Mr Roque said in a statement, promising a fair and thorough investigation by police to bring the perpetrators to justice.