JAKARTA - AN ISLAMIST terror cell discovered in Jakarta this week was planning to bomb the Indonesian capital's main fuel depot and had links to some of the region's most wanted extremists, police said Wednesday.

Police said five suspects had been arrested in and near Jakarta on Tuesday, and weapons and explosives had been seized during a raid on a house in the capital the same day.

'Their target was the Pertamina fuel depot in Plumpang in north Jakarta. It would have been very dangerous if the police had failed to find the explosives,' police deputy spokesman Sulistyo Ishak said.

He said the men were believed to have studied bomb making under Malaysian extremist Azahari Husin, a notoriously callous explosives expert who was tracked down and shot at a house in Java in November, 2005.

Azahari was a close associate of fellow Malaysian Noordin Mohammed Top, the region's most wanted terror suspect who allegedly masterminded the deadly Bali bombings of 2002 and 2005.

'Based on our data and analysis they are suspected of having been Azahari's students because there are similarities in the bomb-making methods,' Mr Ishak said.

'The printed circuit boards they made are more sophisticated than previously,' he said, adding that the bomb-makers appeared to have made 'significant progress' in their designs.

He said there was evidence that various Islamic terror groups had joined forces in Indonesia.

The groups were regional terror network Jemaah Islamiyah's (JI) Indonesian and Singaporean divisions, as well as homegrown jihadi outfits Jundulah, the so-called Islamic State of Indonesia, and others known as KOMPAK and FAKTA.

Top, who has a one-billion-rupiah (S$152,818) prize tag on his head, is believed to be hiding in Indonesia. Police made no comment on any possible links between him and the suspects rounded up on Tuesday.

A raid on a house in a poor part of north Jakarta rented by suspect Rusli Mardani, alias Wahyu Ramadan, netted weapons and explosives, police said.

Mardani had been involved with the militant wing of JI and had links to activities across Indonesia as well as Singapore, they said.

The other four suspects were identified as Muntasir, Hasan, Imam Basori alias Basar, and Budiman who was said to be suffering from thypoid.

JI's hardcore wing is believed to be headed by Top after he split from its mainstream command structure amid differences over the use of extreme violence.

Top is wanted for attacks including the bombings on the resort island of Bali which killed 202 people in 2002 and 20 people in 2005, just a month before Azahari was killed. -- AFP