MANILA, Philippines - A series of killings since the political massacre of 57 people in the southern Philippines last year has set the stage for the country's most violent election in recent history, experts warn.

Politicians defying a government crackdown and running their own mini-armies are one of the key trends behind the political murders, according to independent monitors and officials trying to stem the bloodshed.

"There are just too many private armies, goons for hire and entrepreneurs of violence," Rommel Banlaoi, executive director of the Philippine Institute for Peace, Violence and Terrorism Research, told AFP.

"The government must urgently find ways to deter armed groups and ensure they are not used for election-related purposes."

More than 90 people have already been killed in the run-up to the national elections in May, when thousands of positions from the presidency down to town councilor will be contested, according to the institute.

This includes the 57 people who died on November 23, when a Muslim clan that was then closely allied to President Gloria Arroyo allegedly carried out the murders in Maguindanao province to wipe out a rival politician's challenge.

With the political tensions still to peak, Banlaoi said the Philippines was on track to surpass the 189 people killed in the last presidential elections six years ago, which was regarded as the most violent in recent memory.

"Based on current pre-election trends we are monitoring, 2010 may see the most violent elections in recent history," he said.

Dante Jimenez, a member of a presidential commission created to dismantle private armies following the Maguindanao massacre, offered an equally gloomy scenario.

"There are really expectations that this will turn out to be a very bloody election," Jimenez said.

"People will kill each other because of interests involved. A politician's salary is not that big, but it's not easy to let go of influence and power and the huge business interests that come with it.

"That includes illegal activities."

Jimenez said the commission knew of at least 117 so-called private armies being run by politicians across the country.

The Ampatuan clan accused of the Maguindanao massacre allegedly had about 100 members of its private army carry out those murders, with the victims part of a convoy of people travelling to an election office.

Analysts say the culture of political violence in the Philippines can be partly blamed on rampant gun ownership.

There are more than 1.2 million unlicensed firearms and 1.8 million registered ones, according to police estimates. This means there is an average of roughly one gun for every three Filipinos.

A weak gun control law that allows civilians to carry licensed firearms with special permits has perpetuated the culture of violence, according to Nandy Pacheco, founder of the anti-gun lobby group Gunless Society.

"Buying firearms in the Philippines is like buying candy, it's very easy. And for a certain fee, stores will actually help you process your permit-to-carry license even without checking backgrounds," he said.

Among the dozens of victims in recent months was Joen Caniete, 36, whose death at the hands of anonymous gunmen in December was typical of the way politicians are killed in the Philippines.

Caniete, a member of the opposition Nacionalista Party running for a town councilor post in the northern Philippines, and about 40 colleagues were ambushed as they returned from a Christmas gathering.

Two other Nacionalista Party candidates running for local posts elsewhere in the country were also killed that same week, while a fourth was felled in January.

"The best measure for safety is to really have as few enemies as possible, but there really is no guarantee," Nacionalista Party spokesman Gilbert Remulla told Agence France-Presse.

"If somebody really wants to kill you, they will find a way to do so."