SEOUL - South Korean investigators requested a warrant on Thursday to arrest former first lady Kim Keon-hee on corruption charges, raising the possibility she could join ex-president Yoon Suk-yeol in detention as an investigation against them gathers pace.

The couple are being probed by two separate special prosecutors appointed after the former leader was ousted over his brief declaration of martial law that triggered six months of political crisis and social upheaval.

Kim appeared for questioning on Wednesday at the office of the special prosecutor on charges that include stock fraud, bribery and illegal influence peddling. She apologized for causing concern but did not answer questions from reporters about the allegations.

Oh Jeong-hee, a prosecutor acting as spokesperson for the special prosecutor's team, mentioned three criminal statutes listed on the court warrant request that cover the allegations against Kim but did not give details of the charges.

Kim's lawyers have denied the allegations against her.

A fine art expert who founded and ran a curation agency, the 52-year-old has been the subject of a number of scandals that at times overshadowed her husband's turbulent presidency which ended two years short of a single five-year term.

Yoon, 64, was a career prosecutor who rose to the head of the service before entering politics. He was impeached and removed from office in April and has been on trial on a charge of insurrection and is still under a special prosecutor probe that has widened the scope of the investigation.

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On Thursday, a team of investigators and law enforcement officers armed with a court warrant tried but failed once again to remove Yoon from his prison cell for questioning related to the charges against his wife.

"Based on the opinion from the site that there was a concern for injury because of the zealous refusal by former president Yoon, the execution of the warrant was called off," Oh, the special prosecutor's spokesperson, told a briefing.

Yoon's lawyers described a violent scene as officials tried to move him by force from his cell to a correction service vehicle, describing the attempt as "abusing" a suspect who was exercising his legal right to refuse interrogation.

"(Yoon) pleaded that his arms would fall off and please let him go," one of his lawyers, Song Jin-ho, told reporters. For over an hour, more than 10 "burly young people" wrestled with the former leader and, when they lifted the chair he was sitting in, he was dropped and hit the floor.

Yoon was receiving medical attention at the detention center, Song said.

Oh was quoted by the Yonhap News Agency as saying the officials were executing their duties based on a legal warrant issued by a court and that "minimum force" was used.

The incident was the latest occasion when Yoon has defied authorities during the political turmoil. In January, when he had been impeached but was still president, he ordered presidential security service personnel to block police from arresting him.

Since he was jailed, he has refused to attend his trial on insurrection charges and said through his lawyers he was the victim of a political witch hunt.

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If convicted, he faces up to life imprisonment or even the death penalty for the failed martial law attempt.