Taiwan has formally protested to the World Health Organization after the United Nations agency referred to the island as a province of China, officials in Taipei said Tuesday.

In a reminder of a simmering decades-old sovereignty dispute between the two former rivals, Taiwan's health minister Chiu Wen-ta filed the protest Monday while visiting WHO headquarters in Geneva, they said.

The protest letter to WHO chief Margaret Chan was not made public, but according to a statement released by Taiwan's foreign ministry Chiu asked the WHO to immediately stop labelling the island "Taiwan Province of China".

"Today, we call on the WHO to adopt a fair, sensible, reasonable, and far-sighted attitude, and stop using the false terms 'Taiwan Province of China' or 'Taiwan, China'," the ministry's statement said.

"To end the inconsistency and confusion created by misusing the names, the WHO must use only the name 'Chinese Taipei' in all of its documents, no matter (if) it is internal or external."

When reached by AFP, Peter Cordingley, a Manila-based WHO spokesman, said he could not comment on the protest letter.

Taiwan was invited in 2009 to attend the annual meeting of the World Health Assembly, the highest decision-making arm of the WHO, in the name of Chinese Taipei.

It was the first such invitation since the United Nations expelled Taiwan in 1971 and gave its China seat to Beijing soon after.

The 2009 change was made possible because President Ma Ying-jeou of the China-friendly Kuomintang party adopted a detente with Beijing after taking office in 2008, beefing up trade links and allowing in more Chinese tourists.

Despite the warming ties, China still regards Taiwan part of its territory awaiting reunification, by force if necessary.

It opposes Taiwan's participation in -- or attendance at -- international organisations as a sovereign state even though the island has ruled itself since a split in 1949 at the end of a civil war.

A lawmaker of Taiwan's main anti-China opposition Democratic Progressive Party (DPP) last week released what she said was an internal WHO document obtained from an international organisation.

The memorandum allegedly said WHO communications "must use the terminology 'the Taiwan Province of China'" when referring to Taiwan.