Manila, Jun 16 (IANS): Philippines-based extremist group Abu Sayyaf has threatened to kill another hostage, three days after executing Canadian Robert Hall for non-payment of ransom within the deadline it had set.

"We will upload a new video soon for our new ultimatum. No ransom, another beheading," Abu Sayyaf spokesperson Abu Raami told the Daily Inquirer on Wednesday.

The militants are still holding hostage Norwegian national Kjartan Sekkingstad and Filipino woman Marites Flores on Sulu island, where they had executed another Canadian hostage, John Ridsel, on April 25.

The rebels had abducted the four in September 2015 from a resort in Samal island and demanded around $6.4 million for each of the hostages.

"All I can say is the demand has to be met. Otherwise, we will be executed," Sekkingstad said on the phone.

Since March, when Abu Sayyaf began issuing threats against these hostages, the Philippine Army has unsuccessfully launched several offensives against the rebels.

Philippine President Benigno Aquino, who met with security forces involved in the operations in Sulu on Tuesday said that kidnapping was a very complicated problem and that he understood the difficulties in pursuing Abu Sayyaf.

"If we pay ransom, it would only worsen the problem and encourage others (to engage in kidnapping)," he had added.