Three "gunmen" stormed into the lobby of Crowne Plaza Changi Airport at 4pm yesterday, aiming their pistols at tourists and hotel staff.

And like dominoes, bodies fell as the gunmen sprayed bullets in every direction.

Two of the gunmen then entered the bar upstairs, while the remaining one ran towards the ballroom, shooting at anyone left standing.

But before they could cause more "mayhem", officers from the Singapore Police Force (SPF) and the Gurkha contingent took them down in less than five minutes.

The shoot-out was part of Exercise Heartbeat, which simulates terror attacks. This was the first time the joint exercise by the Ministry of Manpower (MOM) and SPF took place in a hotel.

SPF and MOM have been working closely with hotel industry partners in Singapore to enhance their emergency preparedness and security measures against security threats.

The counter-terrorism exercise yesterday highlights the importance of a robust contingency response plan for hotels against terrorist threats, in the light of the recent hotel and church bombings in Sri Lanka which took place on Easter Sunday last month and claimed 258 lives.

Holland-Bukit Timah GRC MP Christopher de Souza, who observed the exercise, said vigilance is paramount although Singapore has never experienced an attack.

"Events in Sri Lanka brought home to us that we need to be vigilant and respond as one community.

"We need to be diligently prepared, swift in our response and have solidarity in our community after every attack," said Mr de Souza, who is also chairman of the Government Parliamentary Committee for Home Affairs and Law.

Exercise Heartbeat, which started in 2009, has been carried out islandwide in public locations such as the Esplanade and Clarke Quay.

In yesterday's exercise, about 50 personnel from the SPF, Singapore Civil Defence Force (SCDF) and the hotel were involved.

SPF officers worked in tandem with their SCDF counterparts, escorting them as they evacuated casualties.

Hotel staff also helped to administer first aid to casualties, as part of established risk management processes and frameworks put in place at the hotel.

Mr Bruno Cristol, 55, general manager of Crowne Plaza Changi Airport, said: "Participating in this exercise raises our level of emergency preparedness. The safety of our guests and staff is our No. 1 priority."