MANILA -- An international human rights watchdog Tuesday urged President Benigno Aquino III to fulfill his campaign promise to end suspected state-sponsored killings.

Human Rights Watch said four journalists, two leftist activists and a witness to an election-related massacre last year have been gunned down since Aquino was proclaimed the election winner in June. Security forces and gunmen hired by political warlords have been blamed for most of the killings.

Out of hundreds of extrajudicial killings and disappearances in the past decade, only six cases have been successfully prosecuted and 11 people convicted, none of them military members, the New York-based group said in an open letter to Aquino.

Aquino "needs to turn his promises into action by taking immediate steps to end widespread killings and hold the killers and those who deploy them accountable," said Elaine Pearson, acting Asia director at Human Rights Watch.

"In numerous provinces, ruling families use militia forces and local police as their private armies," Pearson said.

The group said the new government should strengthen witness protection programs, abolish private armies and government-armed militias, institute tougher controls on local government procurement of weapons and dismantle "death squads" and investigate government involvement.

Pearson said that Aquino has personally suffered as a result of a government instigated killing and "more than most would recognize that ending such killings would be an important and lasting legacy of his administration." (AP)