Amnesty International has said it is concerned that members of the Philippine security forces might have been involved in a spate of murders of left-wing activists.
Amnesty also said it feared further political killings of civilians were likely and the threat of retaliations by the communist New People's Army would further dim hopes of reviving peace talks between the NPA and the government.
In a report on the Philippines, the group said 51 political killings had been reported in the first six months of 2006, compared to 66 political-related deaths for all of 2005.
Spokesman Tim Parritt said President Gloria Arroyo's failure to stop the killings of human rights workers and peasant leaders could erode public confidence in the rule of law.
Peace talks with the NPA stalled in 2004 when Manila refused to help persuade Washington and some European states to remove the NPA from terror blacklists.
Human rights groups in the Philippines have said close to 700 leftist activists, farmers, students, community organisers and journalists had been killed since 2001 when Ms Arroyo was swept into power by a popular revolt against President Joseph Estrada.
But a national police unit formed by the president to look into the murders said only 114 cases were politically motivated. There have been no convictions despite arrests of suspects in three cases.
