A volcanic eruption in the Philippines has laid waste to homes nearby - an emergency situation exacerbated by a major typhoon hitting the same area within five days.

It is a disaster requiring assistance from around the world, but who will coordinate the effort and how does one make sure resources do not overlap?

Militaries from 18 countries have gathered at Changi Naval Base over the last three days to plan the humanitarian and disaster relief response to this simulated scenario.

The exercise, code-named Coordinated Response, is jointly organised by the Armed Forces of the Philippines, the United States Centre for Excellence in Disaster Management and Humanitarian Assistance, and the Singapore Armed Forces' (SAF) Changi Regional Humanitarian Assistance and Disaster Relief Coordination Centre.

Besides the 18 militaries from countries such as the US, China, Vietnam, Britain and Malaysia, another 12 civilian organisations, such as Doctors Without Borders and the Singapore Red Cross Society, took part as observers.

Defence Minister Ng Eng Hen, who was visiting the exercise area with Philippine Defence Secretary Delfin Lorenzana, said it was "important to have a network of partners, both military and civilian, who are used to working with each other so that you can respond very effectively in the first 48 to 72 hours".

Mr Lorenzana said the exercise was a valuable chance to learn from one another, particularly as his country faces a large number of typhoons in any given year.

SAF's Colonel Lee Kuan Chung, one of the exercise directors, said such drills help link those who want to offer aid to emergency responders in the affected country. "Knowing each other is important so that we don't exchange name cards during the operation... We can exchange them right now," he said.