Singapore as a small country will always be vulnerable, but the nation and people's way of life will be secure if succeeding generations can be convinced of the need to stay cohesive, united and strong, Defence Minister Ng Eng Hen said on Saturday.

He was speaking at the commemoration of the 30th anniversary of Total Defence at the National Museum. He went on to remind Singaporeans to listen to the personal stories of survivors of strife in the country's past, as a way to realise "what happens when our defences fail".

"We should all listen carefully to their stories. Their life stories are cautionary tales that remind us of the heavy price of not being able to defend our country," he said in his address, recounting the often traumatic experiences of several Japanese Occupation and Konfrontasi survivors in the audience.

In his speech, Dr Ng also shared the accounts of conflict survivors such as Mr Zainal Kassim, 75, who was injured in the MacDonald House bombing on March 10, 1965.

Madam Janet Ng, 69, who was also seated in the audience, lost her mother in the same blast. The explosion killed three and injured at least 33.

Interest in Total Defence has risen this year "arising from some episodes in the past weeks", Dr Ng noted without elaborating.

He said: "I don't wish for these episodes (to happen) so that people will listen. But it's a very serious message."

Relations between Singapore and Indonesia have become strained recently after Indonesia named a warship after the saboteurs who bombed MacDonald House.

Earlier in his address, in what are his first public comments on the issue, Dr Ng said that "old wounds have been reopened" by Indonesia's decision to do so.