Abu Bakar Bashir may not be a household name, but the Indonesian cleric is being portrayed as the nearest counterpart in south-east Asia to Osama bin Laden.

Singapore and Malaysia claim Mr Abu Bakar, 63, is the "amir" or leader of Jemaah Islamiah, a regional terrorist organisation whose goal is to create Daulah Islamiah, an Islamic state that would include Indonesia, Malaysia and the southern Philippines.

Under pressure from its regional neighbours, Indonesia has agreed to summon him today for police questioning on alleged terrorist activities.

Intelligence officials say the Jemaah Islamiah (JI), or Islamic Group, represents a serious threat to regional security. They allege it was planning to attack US military and commercial interests in Singapore in December in revenge for the US campaign against the Taliban in Afghanistan.

The arrest of 13 JI members by Singapore's Internal Security Department (ISD) foiled the plan, which was "terribly close to being carried out with devastating results", said a foreign diplomat. "It could have been the biggest terrorist attack since September 11."

Indonesia's sprawling archipelago has been racked by ethnic conflict that has radicalised some Muslims in the wake of the Asian financial crisis and the downfall of Suharto, the autocratic ruler, in 1998. JI's activities and reports of al-Qaeda training camps on the island of Sulawesi have added to worries that Indonesia has become the region's main source for Islamic extremism.

But Jakarta appears reluctant to crack down on Mr Abu Bakar and other Muslim militants because it fears a backlash that would destabilise the fragile coalition government of Megawati Sukarnoputri.

Mr Abu Bakar heads the Indonesia Mujahideen Council, founded 18 months ago to lobby for the adoption of strict Islamic Sharia law in the world's largest Muslim nation.

Singapore said several JI detainees named Mr Abu Bakar as also being the leader of JI. Malaysia has claimed he is the "directing figure" behind the Malaysian Mujuhideen Group (KMM), which has been blamed for bombings and armed robberies.

Mr Abu Bakar has repeatedly denied being involved with the JI or terrorism.

An intelligence official said of Mr Abu Bakar's activities: "Whether he is just serving as [JI's] spiritual leader or is more active is still uncertain."

Hassan Wirajuda, the Indonesian foreign minister, has said Jakarta is still not convinced his country is the base for regional terrorist groups.

"Indonesia does not have the will or the intelligence capability to deal with the terrorism issue," said an Asian intelligence official.

Victor Savage at the National University of Singapore said Indonesia was struggling to suppress separatist movements in the outer provinces. "The military has been put on a back burner and the civilian government is unable to tackle the matter."

Paul Wolfowitz, US deputy defence secretary and a former ambassador to Indonesia, told the New York Times that government control in some areas "extremely weak".

"You see the potential for Muslim extremists and Muslim terrorists to link with those Muslim groups in Indonesia and find a little corner for themselves in a country that's otherwise quite unfriendly to terrorism."

Indonesia's sluggish response contrasts with other nations in the region.

The Philippines has invited 650 US troops as advisers in a campaign against the Abu Sayyef, a Muslim bandit group that has had links with al-Qaeda. Malaysia arrested 47 alleged KMM members. Mr Abu Bakar worked as an Islamic teacher in Malaysia during the 1980s and 1990s, where he fled after a prison term in Indonesia for anti-government activities.

Singapore and Malaysia say some of those arrested trained at al-Qaeda camps in Afghanistan. An al-Qaeda-trained Indonesian explosives expert was arrested last week in the Philippines on suspicion of preparing bombs for the attack on US targets in Singapore.

Intelligence officials admit they do not know the extent of contacts between JI and al-Qaeda or if al-Qaeda played a part in creating JI, which, they believe, was established in 1995 on the island of Java.

Analysts warn that tighter security and surveillance in the wake of the arrests could drive JI and other militant groups further underground.

"They have broken up a few cells but have not rooted out the whole nervous system," said Mr Savage. "How they re-emerge and in what form is the latent security threat the region has to deal with."

Additional reporting by Douglas Wong and Sumathi Bala in Singapore