The threat of terrorism remains very real despite the re-arrest of Mas Selamat, said Singapore's Senior Minister, Mr Goh Chok Tong.

"The fact that he was able to swim away despite our tightened border security following his escape from Whitley Road Detention Centre shows that it is not impossible for a very determined and trained terrorist to enter or leave Singapore undetected," said Mr Goh. He was speaking from a ward in the Singapore General Hospital, where he is recovering from chicken pox.

"From my hospital room, I am reminded that in terms of vigilance, fighting terrorism is like fighting an external virus like Sars or Influenza A (H1N1).

But the best defence against terrorism is still constant vigilance and a domestic environment that is hostile to it, said Mr Goh, who is expected to be discharged later this week.