A state of emergency has been declared in two southern provinces in the Philippines after Monday's massacre in which gunmen killed at least 57 people.

The victims were shot as they travelled to file nomination papers for general elections in May 2010 and their bodies were discovered in a series of shallow graves.

The dead were all civilians, and included journalists and the wife of the vice mayor of Buluan, a town in the Maguindanao province. President Gloria Arroyo's declaration of a state of emergency will mean that police and soldiers can set up roadblocks to help the search for the gunmen.

Longstanding clan rivalry between powerful families in the south lies behind the recent killings. The Mangudadatu clan, members and supporters of which made up the majority of the dead, have made a clear challenge to the politically dominant Ampatuan family ahead of next year's elections.

The massacre was the Ampatuan family's response to that challenge, according to Marites Vitug, editor-in-chief of Newsbreak, a Manila-based news service.

Listen to the Newsline interview with Marites Vitug

"The Ampatuans have been ruling Maguindanao for many years and the Mangudadatu are defying them because they are challenging them in upcoming elections next year...The Ampatuans are a very well-entrenched family, they are backed by paramilitary groups, they are quite wealthy, they control the entire province...this is the first time that there is a major challenge to their regime."

Public outrage
Registrations for the upcoming elections began earlier this month, and while it is not unusual for elections to be marred by violence in the south, this is the first time the bloodshed has been so apparent and caused such public outrage. 

Mrs Vitug says that the central government needs to bring the people behind the killings to justice, but is pessimistic about that happening.

"They should be able to show the justice system works, to gather evidence, prosecute and put the perpetrators behind bars. That's the way to show the central government is strong and that they mean business."

Escaping justice
This is not the first time the Ampatuans have been implicated in political violence. To date not one has been charged or convicted. Because of the scale of the violence there is pressure on the government to do something, despite the fact that clan wars are part of the political system in the Philippines, says Mrs Vitug.
 
"Clan wars are not new in the Philippines, they've been happening since the 1940s and they usually happen at election times and over land conflict. So we expect an escalation which might spill over into neighbouring provinces because so many people were killed. It's unprecedented. We're not sending our reporters based in Manila to cover the event, we have to rely on locals now."

In the unlikely case that the perpetrators are put behind bars, it could lead to an uncontested election, because if the Ampatuan family were to be held responsible, it would leave the Mangudadatuas as the only political clan in the running.