Taiwanese officials say that espionage charges have been filed against a retired air force officer, his wife, and their son, who are accused of spying for China.

Prosecutors in the southern city of Kaoshiung allege that Captain Liu Chen-kuo collected intelligence on Taiwan's military for China after he retired in the late 1980s.

Taiwan and China are continually at loggerheads

They say he and his wife also persuaded their son, a radio decoder in the Taiwanese navy, to use his position to gather sensitive information - including digital photographs of major Taiwanese ports and naval vessels, and details of naval operations systems.

The authorities are seeking a life sentence for Captain Liu, but are requesting lenient treatment of his wife. His son, who is being tried separately by a military court, could face the death penalty.

'Recruited in jail'

Chinese police arrested the elder Liu in 1988 for allegedly smuggling people and antiques out of China and selling forged passports, according to court documents.

Mr Liu spent a year in a Chinese jail before being released a year later on condition that he spy for China, the prosecution statement said.

After his son, 23-year-old Liu Yueh-long, joined the navy in 1997, China asked the father to use his son to gather sensitive material, the statement said.

The court heard that some of the secrets were sent to China by email, while others were carried to the mainland by Liu Chen-kuo.

History of suspicion

Taipei and Beijing have spied on each other ever since they were split by the Chinese civil war in 1949.

In 1999, China court-martialled and executed two of its own officers, Major General Liu Liankun, 58, and Senior Colonel Shao Zhengzhong, 56, for spying for Taiwan.

Communist Beijing considers Taiwan a renegade province and has repeatedly threatened to attack the democratic island if it declares independence.

The two rivals regularly conduct exercises in preparation for possible military combat.