TAIPEI (Reuters) - In rare public comment on territorial disputes in the South China Sea, Taiwan's defense ministry warned on Wednesday that countries in the region were spending more on bolstering their military strength as tension in the area increased.

Taiwan's claim to the South China Sea reflects that of mainland China, with both staking their territorial assertions on maps Chinese Nationalists drew up when they ruled the country before fleeing to Taiwan in 1949.

But Taiwan has stayed relatively low-key on the issue unlike mainland China, which has been backing up its claims with the construction of ports and airstrips on remote islands in the disputed waters.

"Neighboring countries have increased their military budgets and weapons procurement and are adjusting some of their military deployments and conducting joint drills at sea," Taiwan Defence Minister Kao Kuang-chi told parliament as he presented it with his ministry's latest defense report.

Brunei, Malaysia, the Philippines and Vietnam also have overlapping claims to parts of the energy-rich waters through which more than US$5 trillion of maritime trade passes each year.

Last month, Taiwan's defense ministry cautioned "interested parties" to refrain from taking unilateral measures that would increase tension in the area, after it confirmed Chinese forces had deployed surface-to-air missiles on a tiny island in the South China Sea.

The ministry said in its report that Taiwan continued to pay attention to the modernization of China's military, which reflected its determination "to protect its core interest".

Beijing considers Taiwan one of its core interest and sees the island as a wayward province to be taken back by force if necessary.

(Reporting by J.R. Wu; Editing by Robert Birsel)