Phnom Penh police officials met with FBI agents on Wednesday to discuss how the US agency might help in an ongoing investigation into the murders of opposition journalist Khim Sambor and his son.

The two parties reviewed what the Cambodian police have discovered so far and how they will cooperate, said Hy Prou, deputy chief of Phnom Penh police.

"The main point of the meeting required research into how we should conduct the investigation and what we should do first," he said. "But this is a first step."

Khim Sambor, who wrote for the opposition Moneaksekar Khmer newspaper, was killed on July 11, just two weeks before national elections. At least nine other journalists have been killed in Cambodia since 1994, according to the rights group Licadho.

Two FBI agents arrived in Phnom Penh Sunday and will stay for as long as they are needed, US Embassy spokesman John Johnson said.

"They're here to assist in the investigation, depending on the needs of the Ministry of Interior and the Cambodian police that are investigating it," he said, declining to comment on the specifics of the investigation. "The FBI is here to assist in any way possible, and we certainly hope that through this cooperation that the perpetrator of this crime can be brought to justice."

Chan Soveth, an investigator for the rights group Adhoc, said Friday he had little confidence the FBI would be able to find the killer without performing an independent investigation.

"We want the FBI to research this case independently," he said. "If the FBI researches independently, we hope they will find the real killer. But if the FBI researches without independence, I have no hope they will find the real killers."

The FBI also investigated the 1997 grenade attack on a group of opposition supporters, he said, but the investigation yielded no results. In that attack, at least 16 people were killed and one American was injured.

"I don't want the FBI to investigate Khim Sambor's killing like they did in 1997," Chan Soveth said.

Dam Sith, the editor of Moneaksekar Khmer, who was jailed for a week ahead of elections, said he welcomed the collaboration between the FBI and the police.

"I wish to see the real facts and justice without falsehood," he said.

Khim Lenin, 30, the youngest brother of Khim Sambor, appealed to the FBI and the police to find "the real killers of my brother."

"I don't believe the previous report of the police, that the killing was involved with Khim Sambor's son," he said. "As I understand, his son was a good person and never committed any wrongdoings. The same for Khim Sambor."