Former South Korean president Park Geun-Hye's defence lawyers resigned en masse Monday in protest at what they called a biased corruption trial, as the ex-leader described the proceedings as "political revenge".

Park faces multiple charges including bribery, coercion and abuse of power for offering governmental favours to tycoons, and is being held in custody.

She was impeached by parliament after months of mass protests against her over a sprawling graft scandal, and the constitutional court upheld the decision in March, dismissing her from office. She went on criminal trial in May.

The warrant for Park's detention was extended for six months last week, with the court citing the risk that she could destroy evidence if released.

At Monday's hearing all seven of her lawyers submitted their resignations, a court spokesman said.

The lawyers protested at the extension of the warrant, saying that the principle of the presumption of innocence was "collapsing", according to Yonhap news agency.

"As we've reached a conclusion that any defence argument for the defendant is meaningless, all of us decided to resign," one of them, Yoo Yeong-Ha, told the court.

The court asked them to reconsider since the proceedings cannot continue without defence lawyers.

State attorneys will be appointed to defend Park if her own lawyers insist on withdrawing, but the replacement will take time as new representatives would have to review more than 100,000 pages of evidence.

In her first comments to the court since the proceedings began, Park said: "I've come to the conclusion that it's meaningless to believe that the court will handle the case only in accordance with the constitution and conscience", in the face of external political winds and public pressure.

The past six months had been a "horrible and miserable time", during which she had "endured pain in my body and mind".

Park arrived at the courthouse in handcuffs and looking drawn. But she insisted she was innocent.

"I never accepted or granted requests for favours while in office," she said. "I believe it has been fully revealed during the course of the trial that the corresponding suspicions are not true."

She told the court she hoped she would be the last victim of "political revenge in the name of the rule of law".

Park, the daughter of late dictator Park Chung-Hee, is the third former South Korean president to be accused of corruption in Asia's fourth-largest economy, where politics and big business have long been closely tied.

Two former army-backed leaders who ruled in the 1980s and 1990s -- Chun Doo-Hwan and Roh Tae-Woo -- both served jail terms for charges including bribery after they retired.

Another ex-leader, Roh Moo-Hyun, committed suicide in 2009 by jumping off a cliff after he was questioned over graft allegations.

Source: AFP