MANILA (AFP) -- Amnesty International has told the Philippine president that the Melo Commission into political killings must be credible, the human rights group said in a statement Friday.

President Gloria Arroyo met with Amnesty's general secretary Irene Khan in London on Wednesday for what was described as a "frank and constructive dialogue".

Khan welcomed Arroyos' decision to establish the commission and said she should show the same "determined leadership" that saw the end of the death penalty in June to stop "political killings and to strengthen the administration of justice".

Amnesty gave Arroyo a memorandum setting out international guidelines on commissions of inquiries.

Khan said the Commission, headed by former Supreme Court justice Jose Melo, would have to adhere to these standards to gain the "credibility and support of all sides, and carry out its work effectively and independently".

Arroyo created the fact-finding commission last month, following mounting international pressure over the deaths of more than 700 activists since she came to power in 2001.

"Intimidation and violence is still a very real problem and witnesses will not come forward if they are scared for their lives," Khan told Arroyo. "The government needs to provide effective witness protection: victims' families, witnesses and all others involved must be protected."

The military has denied involvement in the killings and charged that communist insurgents were the likely perpetrators of the murders as part of an internal purge.

The presidential palace made no comment on the meeting, preferring to highlight Arroyo's afternoon tea session with Britain's Prince Andrew.

Arroyo was in London to meet with business leaders and to promote the Philippines as an investment centre.