MANILA - Philippine authorities warned Thursday more than 100 private armies controlled by local politicians could cause violence ahead of this year's national elections, as two more candidates were reported killed.

National police chief Jesus Verzosa said a joint study by his office, the military and the Commission on Elections confirmed there were at least 68 "private armed groups" prowling the Southeast Asian archipelago.

"But we have a watchlist which still has to be validated with a total of 102 (private armies). We are watching to see if they take shape," Verzosa told reporters.

Philippine politics has long been plagued by violence and dozens of people are murdered each election season as politicians seek to eliminate rivals' challenges.

Influential clans and families are infamous for their own employing private armies, and police estimate 1.2 million unlicensed guns are in circulation across the country.

Fear about politicians' private armies escalated in November last year when 100 gunmen controlled by a mayor in the southern Philippines allegedly massacred 57 people in a bid to stop a rival running against him.

The government has since vowed to quash the private armies but the violence has continued.

In the latest unrest, Baumol Sula, who was running for town council in the southern town of Banisalan, was shot dead as he was riding his motorcycle on Wednesday, local chief superintendent Josefino Cataluna said Thursday.

Meanwhile, Artemio Tugade, a town council candidate in the northern province of Ilocos Sur, was also gunned down on Wednesday by two motorcycle-riding men, according to a police report.

The killings bring to five the number of candidates murdered in separate incidents in the past two weeks.