In the event of a terror attack, what is most important is that regular citizens know what to do and how to react, Deputy Prime Minister Teo Chee Hean has said.

If they are alert and vigilant, they might be able to prevent and deter would-be attackers from carrying out a strike, he said.

"And if you are caught up in an incident, you have to know what to do. Run, hide, tell, help those around you," he added.

Mr Teo was speaking to reporters yesterday after observing an anti-terror drill - Exercise Northstar - which saw community volunteers and professional first responders work together to respond to a simulated attack.

The four-hour exercise, held at the Home Team Tactical Centre in Mandai, involved about 500 officers from various agencies responding to a scenario of twin car bombs exploding at a mixed-use building housing a shopping mall, a bus interchange and residential units.

Such exercises allow various agencies to test their coordination, said Mr Teo, adding that it was "a very important part to restoring normalcy after an incident".

Led by the Singapore Civil Defence Force (SCDF), the exercise involved key agencies such as the Singapore Police Force, People's Association, national water agency PUB and the Ministry of Social and Family Development.

It was phase two of the 10th edition of Exercise Northstar. Phase one was held on Oct 17 and involved gunmen storming Changi Airport Terminal 3.

MORE NEEDS TO BE DONE

Awareness is increasing. Whether all of our people are fully prepared, I think we are quite far away from that. It's going to be a lot of hard work.

MR K. SHANMUGAM, Minister for Home Affairs and Law, referring to Singaporeans' awareness of the threat from terrorism.

Yesterday's simulated attack saw two bomb-laden cars exploding outside a four-storey building, causing it to partially collapse.

Within an hour, SCDF officers were on the scene, searching through the rubble for survivors. Response efforts were coordinated from an on-site command post.

The SCDF's elite Disaster Assistance and Rescue Team used high-powered drills to punch holes through concrete walls to get to survivors trapped inside.

Meanwhile, search and rescue dogs were sent to comb the wreckage for signs of life.

Some of the rescue operation's heavy lifting was also done by about 200 men from the SCDF's 51 Rescue Battalion, who used wooden beams to shore up unstable walls and help extricate the casualties. This is the first time an operationally ready national servicemen battalion has been involved in the exercise.

Colonel Andrew Tan, commander of the battalion, said the exercise scenario was realistic and that it was challenging to cut through the rubble and get to casualties.

"I think my men are fully aware (of the current security risks) and we need to be prepared to support such emergency operations," said the 46-year-old.

The importance of community volunteers was highlighted by Mr Teo, who said that their actions make a difference.

A community volunteer who took part in the exercise was Madam Chan Shui Ying, 72, who administered first aid to casualties.

She started learning lifesaving skills about 10 years ago, and helps out regularly at grassroots events where people learn skills such as cardiopulmonary resuscitation.

"I tell them, 'Take it up, it's good for your family, you never know when you might need it,'" she said.

Yesterday's exercise was also observed by Minister for Home Affairs and Law K. Shanmugam and Second Minister for Home Affairs Josephine Teo.

Mr Shanmugam said that while Singaporeans understand better the threat from terrorism today, more still needs to be done.

"Awareness is increasing. Whether all of our people are fully prepared, I think we are quite far away from that. It's going to be a lot of hard work," he said.