Militants killed in a raid outside Jakarta on Wednesday had planned to attack a police post in Serpong, South Tangerang, located at a busy intersection.

The police post is across the road from a Giant hypermarket and near the Aeon Mall BSD City, Metro TV reported yesterday.

Police spokesman Martinus Sitompul confirmed this location with The Straits Times in a text message.

Police seized six packets, each containing about two bombs, from a house they raided in South Tangerang - 25km outside Central Jakarta - where three terrorists were shot dead and a fourth arrested, Colonel Martinus told a media briefing yesterday.

An officer with the police Detachment 88 anti-terror squad told The Straits Times that the bombs had been assembled in a different fashion from the ones police usually dealt with, requiring bomb squad personnel to spend more time to safely detonate them.

"Many parts were attached to each other, and these needed to be detached one by one.

"Casings were made out of steel but, instead of straight steel pipes, these were bent, with several short pipes being attached to each other to form one curved pipe," the officer said on condition of anonymity.

Police said on Wednesday that the attack was to have been carried out on Christmas Eve, when more police officers would be deployed in cities across Indonesia.

As many as 155,000 police and military personnel will be deployed from today until Jan 1 to help guard churches and other places where people celebrate year-end festivities, Col Martinis said yesterday.

National police chief Tito Karnavian said separately that one of the terrorists had planned to stab an officer at the police post so that other officers and onlookers would gather around the victim. That would be when two suicide bombers would strike, producing maximum casualties.

A militant named Adam had tipped off police on the whereabouts of his three accomplices, who were killed during a gunfight.

They were identified only as Omen, Helmi and Irwan.

The three men were linked to a terror cell in Solo, Central Java, whose plan to attack the presidential palace in Jakarta was foiled earlier this month.

They were also planning to attack other targets, according to the Detachment 88 officer who declined to be named.

"In August we picked up their conversation. They contemplated attacking the US Embassy but, later, we didn't know what happened to that plan. We hope we can get information from Adam," he said.