MANILA, Nov 30 (AFP) - More than 500 people including journalists and activists marched on the Philippine presidential palace on Monday to denounce the government over the massacre of at least 57 people in the south last week.

Press Secretary Cerge Remonde attempted to address the crowd at a barricade blocking them from reaching the palace, but he was shouted down and pelted with paper by black-clad protesters.

"GMA, you will be held responsible," one placard said, referring to President Gloria M. Arroyo.

Remonde played down the protest, saying he had met with leaders of some activist groups in private to relay that the "government is one with them in condemning what happened in Maguindanao".

"It was okay. Some people were disrespectful," he said.

He said he told the leaders: "President Gloria Arroyo and the government will do everything to ensure that justice is done in the political and media killing."

At least 57 people including a group of journalists were murdered in the southern province of Maguindanao last week by armed men allegedly working for the powerful Ampatuan political clan.

The clan was part of Arroyo's ruling coalition until the president disowned them over the massacre, which killed several relatives of a political rival to the Ampatuans.

So far only one member of the Ampatuan family has been jailed although justice officials say charges are being considered against others.

In an interview with government radio, Arroyo said "what happened in Maguindanao is a black mark against our nation".

"No one will provide a stronger hand in the direction of the nation here in the coming months than me," she said without giving details.