Taipei yesterday protested the Vietnamese government's move to send tourists to the disputed Spratly Islands in the South China Sea, the foreign ministry said yesterday.

In a statement, the ministry said it has voiced serious concerns to Hoang Nhu Ly, Vietnam's representative to Taipei.

The Republic of China is one of the six countries claiming the island group as part of their territories. The other nations are Brunei, China, Malaysia, the Philippines, and Vietnam.

Taiwan has set up a military base on Taiping Island, the largest of the islands that make up the group.

The protest came after a Vietnamese boat carried around 60 Vietnamese tourists and 40 "invited" officials to Big Spratly Island, around 650 kilometers (400 miles) off Vietnam's southeastern coast.

"The Spratly Islands are historically, geographically and legally the territory of the Republic of China, and Vietnamese authorities must immediately halt the move that might cause regional tensions," the foreign ministry said.

Taiwan also renewed its claim to the islands, which straddle vital shipping lanes and are believed to contain vast oil and gas reserves.

In August last year, Taiwan's ex-Interior Minister Yu Cheng-hsien in August raised the national flag on the uninhabited Chungchou Reef, known as Ban Than Reef to the Vietnamese, in a show of Taiwan's territorial claim.

In its latest move, Taiwan's coast guard units on March 23 erected a bird watching observation shelter on a reef six kilometers (3.6 miles) from Taiping Island, despite protests from Vietnam.

Meanwhile China, whose navy has engaged in violent clashes with Vietnamese ships in the islands in the past, has voiced its opposition to the tour.

"This practice by Vietnam violates China's territorial sovereignty," Chinese Foreign Ministry spokesman Kong Quan said in a statement on the ministry's Web site issued on Friday.

Acting Philippine Foreign Affairs Secretary Franklin Ebdalin reminded Hanoi that the 2002 ASEAN declaration of conduct commits signatories "to refrain from committing acts that would disrupt the status quo".

"We have to do this through consultation," he told reporters in Manila. The declaration sets no penalties for violations.

An official from the Vietnam National Tourism Administration told Reuters the tour was a test and, if successful, would be repeated with foreigners, who were barred from the maiden visit.

Vietnam has said the tour aimed to assert its claims to sovereignty over the Spratlys.

The tourists will meet Vietnamese soldiers stationed on the islands, scuba dive at reefs and sail through the Dai Hung oil field. Also on the agenda is a visit to Con Dao, where Vietnam's former French colonial rulers maintained prisons.

Vietnam Defence Minister Pham Van Tra, in Singapore in April, said Hanoi was acting in accordance with ASEAN principles.

The communist country would not be the first to send tourists to the archipelago, he said, citing a similar tour by Malaysia.