Taipei - Taiwan's former president Chen Shui-bian has gone on a hunger strike to protest against his detention over a corruption probe, as Taiwan's High Court upheld a seven-year prison sentence against his son-in-law, officials said Thursday.

"The ex-president has stopped eating since he was placed under custody at the Taipei Penitentiary Wednesday to show his protest against the authorities for political persecution," said his lawyer Cheng Wen-lung.

He said Chen did drink water and his health condition was fine so far.

Chen was remanded into custody Wednesday after his arrest on graft allegations, becoming the first former president to be detained in Taiwan's history.

He is now known as 2630, a number he would be referred to so long as he is kept at the Taipei Penitentiary.

The Taipei District Court ordered Chen detained early Wednesday following an overnight court hearing on a detention request by the Supreme Prosecutor's Office, which questioned Chen the previous day.

The prosecutors wanted Chen detained because his alleged offenses are all major crimes - each carrying a maximum five-year sentence - and out of fear that he might flee abroad.

Cheng said the ex-president, an ardent supporter of Taiwan independence, considered the allegations by the prosecutors politically motivated because the current President Ma Ying-jeou is pro-China and wanted to put him in jail in order to stop the pro-independence movement in Taiwan.

On Thursday, Ma, of the China-friendly Nationalist Party, sternly rejected the accusation, saying he has never instructed the judiciary to do anything against Chen.

Prosecutor Chen Yun-nan, spokesman of the prosecutor's office, also said the judiciary acted independently.

Chen, 57, who became president in 2000 and left office in May, faces allegations including embezzlement of government funds, money laundering, fraud and taking bribes. He sternly denied any wrongdoing.

Meanwhile, the Taiwan High Court upheld a seven-year jail sentence on Chen's son-in-law, Chao Chien-ming for insider trading, adding another blow to the former first family.

Court officials said Chao was sentenced to six years in jail by the district court in 2006 over insider trading of the stocks of land developer Taiwan Development Corp.

They said the high court later increased the sentence to seven years after he appealed against the district court sentence. Chao again appealed to the Supreme Court, which ordered the high court for a retrial in September. Chao can still appeal to the Supreme Court against the latest verdict. (dpa)