Indonesian police confound sceptics with speed as they crack terror cell behind bombing

The clean-shaven young man in a T-shirt and striped shorts appeared supremely relaxed. He laughed and joked with his inquisitors at police headquarters in Bali and – gesturing towards a small crowd of watching reporters – remarked: "Those are the sorts of people that I wanted to kill."

Indonesian police have made such spectacular progress in their investigation of the Bali bombing that they were forced to stage this bizarre public interrogation of their chief suspect, Amrozi, in an attempt to silence sceptics who say he must have been physically mistreated.

Just a month after the explosions that killed nearly 200 people in Kuta Beach, detectives have a key suspect in custody, the names of up to 10 accomplices and a mountain of scientific evidence. The speed with which the case is being solved by a notoriously corrupt and incompetent police force has astonished the Indonesian public as well as British and Australian members of the international investigation team.

The people of Bali are still struggling to absorb the impact of the blasts at two Kuta nightclubs, the worst terrorist attack since the 11 September strikes in the United States. Yesterday thousands of locals attended a Hindu cleansing ceremony at the bomb site, aimed at banishing evil from the island and enabling the spirits of the dead to ascend peacefully to heaven.

Indonesian police, meanwhile, have confounded expectations, partly thanks to the inspired decision to place General I Made Mangku Pastika, one of the country's most highly respected officers, in charge of the inquiry. Within a fortnight of the attack, good luck, diligent detective work and a series of mistakes by the bombers had set police on the trail of Amrozi, 40, a Javanese mechanic.

Amrozi, arrested 11 days ago in his home village of Tenggulun, east Java, has confessed to a sizable role in the 12 October atrocity. He has given investigators a wealth of information about how it was planned and executed and furnished evidence of the bombers' links with international Islamic extremist organisations.

His apparent eagerness to co-operate has roused widespread cynicism in a country that has been awash with conspiracy and cover-up theories since the explosions. But, judging from his public appearance in Denpasar, the Balinese capital, on Wednesday, he seems to be in good health – apart from a black eye.

Police got their first break an hour after the three blasts when a bystander alerted them to a red Yamaha motorcycle parked outside a mosque in Denpasar. The bike, it appeared, had been used as a getaway vehicle by the person who left a white Mitsubishi minivan packed with explosives outside the Sari Club.

The bike's tail light had been disconnected, presumably so the number plate was not visible as it sped away; chemical residues associated with the explosives were found under the seat. Police traced the salesman, who had sold it to three men several days earlier, and used his descriptions to compile sketches. Another notable mistake made in a highly professional operation was Amrozi's clumsy attempt to disguise his identity by having his hair cut twice in Tenggulun in the week after the attack.

But the biggest breakthrough was a result of the bombers' sloppiness in concealing the origins of the minivan. Rather than stealing a vehicle, they used one recently bought by Amrozi and registered in his name. They changed its chassis number, but police tracked it through a second serial number required to be stamped on all vehicles used for public transport.

During his first 40 hours in custody, Amrozi refused to crack. Then police showed him receipts for 1,100lb of bomb-making materials that he had bought at a chemical supply shop in Surabaya, east Java. Confronted with the serial number connecting him to the van, he broke down and confessed.

Since then, the information has been tumbling out at a pace that has startled even police. General Pastika, who was allowed to hand-pick his detectives for the inquiry, said: "I understand people don't believe what we have reached in a short time." Of Amrozi's arrest, he said: "We were lucky."

General Pastika, who served as a commanding officer for United Nations police in Namibia in the 1980s, has a reputation for integrity in a country where corruption is entrenched. Fluent in six languages, he won respect for standing up to the Indonesian military in the troubled province of West Papua.

He has been cautious in his assessment of the bombers' links with the al-Qa'ida network and Jamaah Islamiya (JI), the regional extremist movement suspected of carrying out attacks in South-east Asia. But security sources think the bombing was conceived after a meeting in Thailand in January chaired by Riduan Isamuddin, alias Hambali, thought to be JI's operations chief.

Amrozi said the planning began in August and much of it took place in Solo, the central Java city that is home to Abu Bakar Bashir, the radical cleric suspected of being JI's spiritual leader. He told police that the team subsequently communicated via mobile phone text messages and gathered in Malaysia in early October before heading to Bali.

Amrozi has admitted to a close friendship with Mr Bashir, who often visited Tenggulun, location of an Islamic boarding school founded by Amrozi's family. Police have raided the Al-Islam school, where boys were reportedly taught hand-to-hand combat and weapons handling. Rifles were seized from an adjoining house.

Amrozi's precise status within the group of bombers remains unclear. Police have described him as a field co- ordinator and "second tier" facilitator. Other members of his family may have played more significant roles. Police believe his elder brother, Mukhlas, leads JI's Malaysian and Singaporean unit and may have recently replaced Hambali as operations chief.

Amrozi has told police he was recruited to the Bali plot by a younger brother, Ali Imron. As he tells it, he was a juvenile delinquent led astray by his siblings.