A brother-in-law of former President Chun Doo-hwan was formally detained Monday to undergo further questioning over allegations that he evaded taxes in a land transaction to let Chun's children gain a profit.

Lee Chang-seok was put under detention immediately after the Seoul Central District Court approved the prosecution's request for an arrest warrant. The 62-year-old is alleged to have played a crucial role in illegally transferring wealth from Chun to his two sons.

It marks the first time that any family member of Chun was put behind bars since the prosecution office launched a probe team tasked with reclaiming the fortune of the former military dictator who was convicted of taking bribes while in office in the 1980s.

"(Lee's) crimes have been ascertained, and there is a reasonable concern that the suspect might attempt to destroy evidence or flee," Judge Kim Woo-soo said in issuing the warrant.

Chun was ordered by the nation's top court in 1997 to return to state coffers some 220 billion won ($196.8 million) he illegally accumulated through bribery from big businesses during his military rule in 1980-88.

Chun, who seized power through a coup, has refused to make the payment, with some 167.2 billion won remaining unpaid.

Suspecting that Chun stashed his fortune in paper companies and bank accounts associated with family members, prosecutors have been zeroing in on not only his immediate family members but also his in-laws.

Lee, the younger brother of former first lady Lee Soon-ja, is suspected of having evaded taxes in a transaction in 2006, in which he sold his 460,000 square meters of land in Osan, just south of Seoul, to Chun's second son, Jae-yong, at a price of just one-tenth of the officially appraised price, prosecutors said.

The Seoul Central District Prosecutors' Office alleged that Lee evaded transfer and gift taxes worth some 10 billion won in the process.

The land might have also been allegedly purchased with illegal funds from Chun, prosecution officials said.

There has been a public outcry about the delay in collecting the unpaid fines from the 82-year-old Chun, who has repeatedly claimed that he is penniless.

Chun's lawyer, in documents he submitted to the court, said the former president used nearly all of his money for political purposes while in office. The assets now in Chun's family, according to the lawyer, were inherited from his father-in-law before the presidency. (Yonhap News)