HANOI, Vietnam - Vietnam on Thursday hit back at Taiwan for taking international media on a tour of a disputed island in the South China Sea, saying the "illegal and worthless" trip had further raised tensions in the hotly contested waters.
Taiwanese officials on Wednesday took journalists to Taiping, the largest island in the Spratlys chain, which it controls and views as part of its territory.
The Spratlys are also claimed in part or whole by China, Vietnam, the Philippines, Malaysia and Brunei and have been at the centre of escalating rows.
"Taiwan, despite concerns and objections from Vietnam and the international community, sent journalists to Taiping Island," Foreign Ministry spokesman Le Hai Binh said in a statement.
"This is a serious violation of Vietnam's sovereignty, escalates tensions and is not conducive to maintaining peace and stability in the South China Sea."
A visit to Taiping by Taiwan's President Ma Ying-jeou in January triggered criticism from the United States which described it as "extremely unhelpful", as well as protests from Vietnam and the Philippines.
The Philippines is currently in the midst of an arbitration case against China at the Hague over the South China Sea. A ruling on the case is expected before May.
As part of its case, the Philippines argues that Taiping and other islands are just "rocks", a categorisation which helps its broad claims in the area.
Taiwan disagrees, saying Taiping is a fully fledged island, a designation which entitles it to a 200-nautical-mile exclusive economic zone.
On Wednesday, journalists were shown facilities including a hospital, post office and temple, as well as visiting a monument engraved with the words "Taiping Island" during the three-hour visit.
"Any activities by foreigners carried on the two island chains and not approved by Vietnam are illegal and worthless," Binh added.
Rival claimants in the South China Sea have been beefing up their military presence in the disputed region, and other countries have complained China is becoming increasingly aggressive in pressing its case.
Beijing has reclaimed more than 2,900 acres of land in less than two years in an intensive island-building campaign and has deployed surface-to-air missiles on a disputed island there, according to Taipei and Washington.
Other claimants, including Vietnam, have carried out reclamation work on islands they control, but the scale and pace is dwarfed by that of Beijing.
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