WASHINGTON (REUTERS) - The US Federal Bureau of Investigation said on Wednesday it has confirmed that Zulkifli Hir, known as Marwan and one of its "most wanted terrorists," was killed in a raid in the Philippines in January.

The US State Department had offered US$5 million (S$6.8 million) for the arrest of Zulkifli, a Malaysian member of the Al-Qaeda-linked Jemaah Islamiah militant group behind numerous bombing attacks in the Philippines.

Investigators said they had a difficult time confirming Zulkifli's death because he was killed in a gruesome raid that went awry and left 44 police commandos dead.

Previously, the FBI reported that it had identified body matter at the scene that it believed belonged to Zulkifli because of a DNA link between the matter and one of his siblings.

Three years ago, the Philippine military reported Zulkifli died in an air strike, but he surfaced again last year in Mindanao under the protection of a Moro Islamic Liberation Front splinter group.

In a statement, Mr David Bowdich, assistant director in charge at the FBI Los Angeles Field office said the agency has now taken Zulkifli off its Most Wanted Terrorist list and thanked the Philippine police.

"Once again, the men and women of the FBI express sincere condolences to the brave officers of the Special Action Force who lost their lives while attempting to apprehend this dangerous fugitive," Mr Bowdich said.