BEIJING, Sept 29 (Reuters) - China on Wednesday accused Taiwan Premier Yu Shyi-kun of clamouring for war with threats to fire missiles at Shanghai if the People's Liberation Army (PLA) attacks the self-ruled island.

Yu last week defended plans to buy T$610.8 billion (US$18.2 billion) worth of weapons from the United States, saying Taiwan needed a counter-strike capability to hit China's financial centre of Shanghai with missiles if the PLA attacked the island's capital, Taipei, and the southern city of Kaohsiung.

"Yu Shyi-kun's remarks are a serious provocation and clamouring for war," Li Weiyi, spokesman for the policymaking Taiwan Affairs Office, told a news conference.

Many security analysts see the Taiwan Strait as the most dangerous flashpoint in Asia. China claims sovereignty over Taiwan and has threatened to attack the democratic island of 23 million people if it formally declares independence.

Beijing and Taipei have been rivals since their split at the end of the Chinese civil war in 1949, but trade, investment and tourism have blossomed since detente in the late 1980s.

"For the Chinese people, there is nothing more important, more sacred than safeguarding national sovereignty and territorial integrity," Li said.

"Any person, any force using whatever methods to attempt to seek Taiwan independence and make enemies with 1.3 billion Chinese people is doomed to failure," he said.

By arming itself, the island was seeking nationhood, he said.

Tensions between China and Taiwan have been simmering since the March re-election of the island's President Chen Shui-bian, who Beijing is convinced will push for statehood during his second four-year term.

Taiwan's weapons package is made up of $4.3 billion for Patriot Advanced-Capability 3 missile defences, $12.3 billion for eight diesel-electric submarines and $1.6 billion for 12 P-3C Orion submarine-hunting aircraft.

Washington switched diplomatic recognition to Beijing from Taipei in 1979 but remains the island's biggest arms supplier.

Chen said last week China had 610 missiles pointed at Taiwan, up from 496 last December, and that China's arsenal was increasing by 50 to 70 missiles every year.

Thousands of protesters marched through Taipei on Saturday, urging their government to scrap the weapons package they said would trigger an arms race with China and squeeze social welfare.

In a speech before the protest, Yu said: "If you attack me with 100 missiles, I will at least attack you with 50. If you attack Taipei and Kaohsiung, I will attack Shanghai.

"If we have such counter-strike capability today, Taiwan is safe," he said defending the arms deal.

Taiwan's opposition parties, which hold a slim majority in parliament, said the island could not afford the weapons and the money should be spent on social welfare or education.

The package has come under growing criticism in Taiwan, with opponents charging that the weapons are too costly or take too long to deploy to be an effective defence.

Taiwan's military says the package will help to maintain a balance of power with China for another 30 years. If it falls through, it says, the PLA will have the capability to overrun the island in the next two to three years.