A MASSIVE manhunt involving thousands of policemen and Gurkhas was launched yesterday after Mas Selamat Kastari, the terrorist who planned to crash a hijacked plane into Changi Airport, escaped from detention.

Mas Selamat, 47, who took over as head of the Jemaah Islamiah (JI) terror network here in 1999, fled the Internal Security Department's Whitley Road Detention Centre at 4.05pm yesterday.

The hunt began soon after, with police, Gurkha and Special Operations Command officers fanning out several kilometres from Goldhill Avenue, near Barker Road, to the Beauty World shopping centre in Upper Bukit Timah Road.They formed a perimeter at Malcolm Park, near the Singapore Chinese Girls' School (SCGS), facing the wooded area.

Late last night, officers with flashlights were seen going house to house along Malcolm Road, near St Joseph's Institution and behind Catholic Junior College, questioning residents and checking the leafy neighbourhood.

Elsewhere, officers stopped vehicles at roadblocks, questioned residents, and showed pictures of Mas Selamat.

The alert also went out to all border checkpoints, the Police Coast Guard, and even taxi companies, which broadcast a message to cabbies telling them to look out for the suspect.

Scores of plainclothes police officers also swarmed convenience stores and petrol stations, going through CCTV footage for any glimpse of the wanted man.

An SCGS teacher said school staff were also questioned.

The lockdown, from late afternoon through the night, gave the whole area an almost surreal feel, with scores of police vehicles flashing blue and white lights lined up along the roads.

There were roadblocks at several areas, and grim-faced personnel, their neon green work vests glowing in the glare of lights, checked car boots and spoke urgently into walkie-talkies.

The huge uniformed presence signalled immediately to residents of the affected areas that something big was going on.

Mrs Jasmine Lim, 42, whose car was checked as she entered Goldhill Estate where she lives, said some residents were worried.

The mother of four said she called her two older children, aged 22 and 19, and told them to get home early. 'I have a security alarm that I normally don't activate so early, but tonight I will,' she said.

Senior accounts manager Terry Chia, 44, said police stopped him on his way home and showed him a picture of Mas Selamat.

He did not think anything of it at the time, but said he began to worry when he learnt that the escapee was a JI detainee.

The Ministry of Home Affairs issued a brief statement yesterday about the escape. It said Mas Selamat walks with a limp, and was not believed to be armed.

The Indonesian-born JI leader escaped a dragnet that resulted in the detention of 13 JI members here in December 2001. The group had been planning to attack targets here.

While in hiding, Mas Selamat plotted to hijack a plane and crash it into Changi Airport. The plot was foiled.

He was arrested in Indonesia twice, before being handed over to Singapore in February 2006, and has been detained under the Internal Security Act since March that year.

As The Straits Times went to press at 1.30am today, there was still an overwhelming police presence in the Bukit Timah area.