MANILA - The massacre of at least 46 people in the southern Philippines has exposed a brutal culture of guns, greed and money that for decades has poisoned the nation's political system, experts said Tuesday.

The murders in the province of Maguindanao on Monday are feared to be only the first of many killings likely ahead of next year's national elections, when posts from village chiefs to president will be up for grabs.

"This explosion of violence arises whenever there is an election," said Samira Gutoc, one of the leaders of the Young Moro Professionals, a group helping the government in peace talks with armed Muslim groups in the south.

Indeed, dozens of people are killed each election season in this impoverished and often lawless Southeast Asian nation.

Local political warlords have for generations competed for political power and the accompanying business riches that government posts offer.

These clans are widely known to control private armies, which carry out assassinations and counter-attacks against rivals.

The proliferation of over 1.1 million unlicenced firearms, most of them in the hands of rebel groups or paramilitaries, contributes to the general lawlessness in many remote areas, according to police.

In one high-profile murder in the run-up to congressional elections in 2007, a hired assassin gunned down a member of parliament from a northern province on the steps of a Manila church as the politician attended a wedding.

All in all, 121 people were killed in that polling season, according to national police statistics, slightly lower than the 148 who died in the 2004 national elections.

But while the problem plagues the entire country, experts say the situation is particularly volatile in Maguindanao and other parts of the far southern island of Mindanao, where a Muslim insurgency has raged for decades.

"Politics in Mindanao is about ownership of power. Public office is perceived as a personal, clannish thing -- a birthright, and they would spill blood for it," Gutoc said.

She said she expected more violence in the fallout from Monday's massacre, with relatives of those killed likely to carry out vendetta killings, called "rido" in the local dialect.

"Retaliation is a natural course of events," she said.

At least 46 people were murdered as they accompanied the wife of local official Esmael Mangudadatu to file his candidacy for governor of Maguindanao, as he bid to end the decades-old control of a rival Muslim clan.

The military said 100 heavily armed men under the control of his rival, Andal Ampatuan, seized the group and later shot them.

Forty-six bodies have so far been found, police said.

The military said the Ampatuans were the prime suspects in the massacre.

Abhoud Syed Linga, executive director of the Institute of Bangsamoro Studies and an expert on clan fighting, said the revenge culture complicates the Muslim insurgency, which has claimed more than 150,000 lives since the 1970s.

"Some rido are sustained for generations," Linga said. "The retaliation and counter-retaliation involve the whole family or clan."

The vendetta killings, he said, are the "consequence of the absence of justice" for a perceived wrong.

"Among Muslims the value of justice is strong, to the extent that it becomes a duty for family members to work for justice and reject oppression," he said.

Amnesty International said the killings underlined the danger facing civilians across the entire country in the lead-up to next year's elections.

"The government must prohibit and disband private armies and paramilitary forces immediately," said Amnesty's deputy director in Asia, Donna Guest.