Mark Baker in Manila and Lindsay Murdoch in Jakarta – The Indonesian Government is under mounting pressure to crack down on the fundamentalist Jemaah Islamiah movement after new evidence linking it to Osama bin Laden's al-Qaeda network and terrorist raids across South-East Asia.

Authorities in the Philippines, Singapore and Malaysia believe that members of the movement – led by the cleric Abu Bakar Bashir and backed by al-Qaeda chiefs – were responsible for a foiled plot to attack Western targets in Singapore, including the Australian High Commission.

Bashir, who is being questioned by Indonesian police after Singapore and Malaysia demanded his arrest, has denied involvement in terrorism but has expressed sympathy for bin Laden and al-Qaeda. After a police interview on Thursday, he lauded bin Laden as "a true Islamic warrior" who had shown the courage and skill to fight the United States.

Philippines intelligence officials believe the foiled Singapore attacks were planned by an Indonesian activist, Fathur Rohman al Ghozi, who was arrested in Manila last week. They say al Ghozi is a member of the Moro Islamic Liberation Front, which bombed a Manila railway station in 2000, killing 22 people. He has also been linked to bombings in Indonesia.

The director of the Philippines National Police Intelligence Group, Chief Superintendent Robert Delfin, says of al Ghozi: "He is the missing link between the Philippines terrorist group and the Singapore group. He is a key figure."

Singapore authorities say the planned attacks on Western targets were confirmed by a surveillance videotape found in the wreckage of an al-Qaeda leader's house in Afghanistan in December.

Since the arrest of al Ghozi, Philippines authorities have also detained four alleged Filipino accomplices and seized weapons and explosives from a house rented by him. They say the explosives were to be smuggled to Singapore via Indonesia. However, Indonesia has so far been reluctant to vigorously investigate links between Bashir and al-Qaeda.

Bashir told journalists that even after four hours of questioning in Jakarta, police had not asked him whether he was connected to al-Qaeda. On Thursday, the Indonesian Foreign Minister, Hassan Wirajuda, said claims of links between al-Qaeda and local Muslim elements were still "indicative".