The Pentagon has evidence that the Chinese military has deployed surface-to-air missiles on an island in the South China Sea, a U.S. official said Tuesday night.

The deployment escalates tensions in the region and comes after officials in Beijing pledged not to militarize islands in the sea, where China's territorial claims are disputed by several nations.

The official said the Chinese appear to have deployed HQ-9 missile systems on Woody Island in the Paracels, which is claimed by China, Vietnam and Taiwan. Taiwan's defense ministry, in a statement, confirmed Wednesday morning that China had placed anti-aircraft missiles on the island.

The U.S. official, who requested anonymity to discuss intelligence matters, did not comment on when the missiles might have been deployed, how many there were or whether they were operational.

The missile deployment was first reported by Fox News, which said pictures from ImageSat International showed that the missile systems appeared on the island sometime between Feb. 3 and Sunday.

The Chinese-made Hongqi-9 missiles have a range of about 124 miles and are capable of destroying aircraft and other missiles. Word of the deployment came as President Barack Obama was concluding a summit meeting with leaders from the Association of Southeast Asian Nations in California.

Several member nations, including Vietnam and the Philippines, have expressed concern over China's efforts to construct artificial islands in the Spratlys, low-lying islands, reefs and shoals that lie to the southeast of the Paracels.