Singapore's Mass Rapid Transit (MRT) stations are being patrolled by armed police personnel who may 'shoot to kill' suspected suicide bombers.

The move was the republic's response to possible threats in the wake of the July 7 bombings of central London's transportation system that killed over 50 people and injured dozens of others.

According to a Bernama report, officers have been patrolling in pairs since yesterday and other specialist units may also be activated to deal with the situation.

The officers, from the police MRT unit, will also be conducting checks on bags and other items on board trains, said the report quoting television station Channel NewsAsia.

On whether these officers would shoot to kill in the face of potential threat, Home Affairs Minister Wong Kan Seng said, "Yes, they may have to".

"We have to evolve our rules of doctrine according to the circumstances. In our context today, we have not come across a suicide bomber case and we hope we will not come across one," he said.

"But I would not rule this out because suicide bombing is one of the preferred techniques of the terrorists to frighten and intimidate normal citizens."

An estimated 1.2 million people commute using MRT and light rapid transit (LRT) services daily in Singapore.

'Brace yourselves'

Last month, Deputy Prime Minister Tony Tan said Singaporeans must brace themselves for the possibility of a terrorist attack.

"How we act after a terrorist attack will be a big test for our strength and courage as citizens," he had told a Parliamentary security briefing.

He said although the Internal Security Department did not have any specific intelligence report on an impending terrorist attack, "we must remember that Jemaah Islamiah had previously planned to attack MRT stations".

Jemaah Islamiah is allegedly linked to Osama bin Laden's al-Qaeda terror network and is said to have members in Indonesia and Malaysia.

The threat of terrorism has loomed above the republic due to its close ties with Israel and the United States.