It was not escaped terrorist Mas Selamat Kastari, who broke out of jail on Wednesday, but rather, a Sri Lankan man in his late 20s.

The officers arrested the illegal immigrant at 6.30am when they were conducting stepped-up checks on vehicles leaving the country.

The Malaysian bus driver, who in his late 20s, was also arrested.

The 40-seater bus was not carrying any passengers nor any luggage.

Deputy Superintendent Tan Kong Hui, the deputy commander for counter-terrorism and security, said: 'When we first found him, it is natural that we had linked him to the terrorist because that is who we are all looking for.'

According to DSP Tan, preliminary investigations show that the illegal immigrant is not linked to Mas Selamat.

But he is the first suspicious character arrested trying to leave Singapore illegally at the Woodlands Checkpoint since the manhunt for the former Jemaah Islamiah leader started three days ago, said DSP Tan.

Immigration checkpoints have been put on high alert for the missing terrorist.

At the Woodlands Checkpoint yesterday, the police conducted thorough checks on all vehicles, including the boots. Drivers were also asked to step out of their vehicles.

Before the high alert, only random vehicles were searched. Now, every vehicle is put through a check.

DSP Tan said: 'We will examine each and every vehicle and not spare a single one.'

Such stepped-up checks have caused some delays for travellers waiting to clear the checkpoints.

There were massive traffic jams at both checkpoints in Tuas and Woodlands during the evening peak hours on Thursday, with some waiting for as long as an hour to get to Malaysia.

There was also a slight jam at the Woodlands Checkpoint yesterday morning.

DSP Tan appealed for the public to be 'more understanding'.