A shootout outside an airport in central Taiwan apparently sparked by a man who punched a policeman killed one person and left two others wounded, police said.

The rare exchange of gunfire occurred at around 2:40 pm (0640 GMT) when a man who was taking his 10-year-old daughter to Chinchuankang airport confronted a policeman for not wearing a helmet.

Taiwanese prosecutors on Friday indicted a Chinese man on suspicion of recruiting a former major-general and other local military officers to spy for Beijing, in the latest of a string of espionage cases to hit Taiwan.

Five Taiwanese military officials, including retired major-general Hsu Nai-chuan, were also charged with violating national security law together with Chinese Zhen Xiaojiang, said the Taipei district prosecutor's office.

The United States on Tuesday denounced a flag-raising ceremony at Taiwan's de facto embassy in Washington, saying it violated a long-standing pact on U.S.-Taiwan ties.

"We're disappointed with the action," State Department spokeswoman Jen Psaki said when asked about the hoisting of the Taiwanese flag at the compound on New Year's Day.

A 5.5-magnitude undersea earthquake struck Taiwan Wednesday and shook buildings in the capital, but there were no immediate reports of casualties or damage.

The quake struck at 3:54 pm (0754 GMT) with its epicenter 87.5 kilometers (54 miles) southeast of the northeastern city of Yilan at a depth of 83.1 kilometers, the central weather bureau said.

Taiwan said Monday it was launching a project to build a fleet of its own submarines, after years spent waiting in vain for U.S. models.

Taiwan's former vice-president started a hunger strike Sunday as part of a growing campaign for the release from prison of ailing ex-leader Chen Shui-bian.

Chen, now 63, who led the opposition Democratic Progressive Party (DPP) to power in 2000 after 50 years of Kuomintang rule, is serving a 20-year sentence for corruption.

The sole leadership candidate for Taiwan's ruling party said Sunday he would keep pushing for stronger ties with China even though its Beijing-friendly policy was blamed for its worst-ever local election setback.

"The development of cross-strait ties will continue," Eric Chu, incumbent mayor of New Taipei City, told reporters after registering with the Kuomintang (KMT) party for chairmanship elections slated for January 17.

China on Friday said it had lodged a formal complaint with the United States over its approval of frigate sales to Taiwan and called for an end to arms sales to the island Beijing claims as a renegade territory.

Prosecutors said deadly gas explosions in Taiwan were caused by "multiple human errors" Thursday as they charged 12 people over the blasts, including the head of a chemical company and government officials.

The disaster killed 32 people and wounded more than 300 in southern Kaohsiung city as explosions in underground pipelines sparked massive fires on July 31 and left trenches running down the middle of some streets, with vehicles thrown onto the roofs of buildings.

A visiting Chinese envoy was quoted Wednesday as saying relations with Taiwan will not be damaged by the landslide defeat of the island's Beijing-friendly Kuomintang ruling party in local elections.

The eight-day trip by Chen Deming, president of China's quasi-official Association for Relations Across the Taiwan Straits, comes amid growing fears about China's increasing influence in Taiwan.