At a night market where two children are queueing to buy food, a suicide bomber detonates the explosives on her body.

Minutes later, another bomb goes off just metres away, where an unattended parcel was lying.

When the survivors scurry for shelter at a nearby car showroom, two bigger bombs go off there.

These were the scenarios posed to police investigators from Singapore and Brunei at a biennial exercise to hone the their post-blast investigative techniques.

The media had been given access, for the first time, to the three-day Solar Wind exercise in Brunei which ended yesterday.

Unlike previous iterations, this year's exercise was the most complex as it featured multiple bomb attacks at different locations, said Mr Sito Wai Yip, officer in charge of the Singapore Police Force's bombs and explosives branch.

The exercise mimicked real-life incidents like the Sri Lankan bombings earlier this year, when suicide attackers carried out simultaneous strikes in different locations, Mr Sito told the media.

One takeaway for the investigators was how to coordinate their efforts with each other, he said.

"This coordination is the most difficult, as inputs (like evidence) from each scene must be communicated in a timely manner, so that we will not lose track of the perpetrators," said Mr Sito.

"We hope the officers will become more familiar with their procedures and drills, and gain more useful on-the-ground experience," he added.

To simulate urban conditions, mannequins, wooden stalls, a car and a motorcycle were set up in a field in Brunei, and around 30kg of explosives were detonated at the two scenes.

Investigators were kept in the dark about the nature of the explosions, and they had to develop their hypotheses for the blasts by processing and looking at evidence such as the bomb fragments, size of craters in the ground as well as explosive residue.

They also had to practise processing a scene efficiently, as investigators typically have to clear a bomb site within a day so as to restore normalcy and bolster the public's confidence, according to Mr Sito.

Brunei's Assistant Commissioner of Police, Dato Paduka Haji Mohammad Hassan Pehin Penyurat Haji Ahmad, said such exercises have helped to build and strengthen the rapport between the two countries.

The Solar Wind exercise started in 2014, and the latest drill was its fourth edition.

"We need to continue this so we can exchange expertise and learn from each other's experience and be prepared, especially with the current (terrorist) situation in the region," he said.

Singapore's Assistant Commissioner of Police Shee Tek Tze said post-blast investigations are an important capability for the police force, especially as terror threats remain high.

"We monitor incidents around the world and learn what are some of the new modus operandi adopted, so we can prepare ourselves to respond to such incidents in Singapore," he said.

Having a realistic training scenario with real bombs, as was done in this exercise, helps ensure that officers are operationally-ready, said Mr Sito.

"While real-life experience is a bonus, what is essential at the end of the day is subject-matter knowledge such as the correct investigation tools. This can be achieved through training," said Mr Sito.

And he reiterated the SGSecure slogan: "A bomb incident is not a matter of if, but when".