At least 39 people are now known to have died in the southern Philippines on Monday, after more bodies were discovered in a shallow grave.
Philippine President Gloria Arroyo has declared a state of emergency in two provinces on the island of Mindanao to allow police to search for the gunmen.
The victims were killed as they were travelling to file nomination papers for elections next May, BBC News reports.
According to New York Times, the president of the Philippines on Tuesday declared a state of emergency in the southern region where gunmen kidnapped more than 40 people and killed at least 35 of them, military officials and news agencies reported.
In one of the worst episodes of election-related violence in the Philippines, a group of lawyers, journalists and relatives of a local politician was kidnapped Monday in Maguindanao, a province on the southern island of Mindanao.
Lt. Col. Romeo Brawner, a military spokesman in Manila, the capital, said 21 bodies had been recovered on Monday, and search teams on Tuesday reportedly found 14 more bodies in fresh graves that had been dug with bulldozers.
The government ordered the police and military to "prevent and suppress all lawless violence" in Maguindanao province, where yesterday’s attack took place, Press Secretary Cerge Remonde told reporters in the capital, Manila. The decree also covers the province of Sultan Kudarat and Cotabato City.
"No effort will be spared to bring justice to the victims and hold the perpetrators accountable," Arroyo said at the start of a Cabinet meeting today. She deployed extra troops and ordered the national police chief to lead investigations into the killings, Bloomberg informs.