PORAC, Pampanga, Philippines?President Gloria Macapagal-Arroyo has declared Thursday as a national day of mourning as the nation confronts one of its bloodiest election-related atrocities following the killing of at least 52 people, including journalists, in Maguindanao, last Monday.

The President first announced the declaration in her visit to her home province on Wednesday to open a P360-million access road connecting this town to the Subic-Clark Tarlac Expressway (SCTEx).

?I am outraged as is everyone at this crime. It is a travesty of our pledge to uphold the basic humanity of every Filipino," Arroyo said.

She vowed to make sure that the people behind the murders not escape justice ?because the law will haunt them until they are caught.?

?Commitment to human rights and human dignity shall prevail in the Philippines," Arroyo said.

At least 52 people, mostly women and journalists, were killed when armed followers of a political clan in Maguindanao waylaid them on Monday.

The victims, who included women from the Mangudadatu family, were on their way to the Commission on Elections office in Shariff Aguak town to file the certificate of candidacy for governor of Buluan Vice Mayor Esmael Mangudadatu when their vehicles were blocked by armed men.

Some of the victims were ordered to alight from their vehicles and were shot and killed. Some were shot dead right inside their vehicles.

In a statement read for her by Ermita at Malacañang, Arroyo said, "I am declaring a national day of mourning in honor of the victims. This crime is too outrageous not to prick the conscience of this nation or any other nation for that matter. Let us hope that the outrage is overcome by reason and by our need to live our lives in peace, honor and human dignity."

Ermita said black ribbons would be tied at the Palace grounds as a show of commiseration for members of the Mangudadatu clan, their supporters, journalists, and other civilians massacred by suspected followers of the Ampatuan family in Maguindanao.

"This is not a simple election feud between opposing clans; this is a supreme act of inhumanity that is a blight on our nation," Arroyo said. "The perpetrators will not escape justice. The law will hunt them until they are caught."