Seoul, Sep 21 : South Korea's impeached President Yoon Suk Yeol has requested to be released on bail, citing the need to prepare his defence and health concerns, according to legal sources on Sunday.

The application was filed on Friday with the Seoul Central District Court, which is handling charges against him for obstruction of duties and abuse of authority. A date for the bail hearing has not yet been set, Yonhap News Agency reported.

Yoon has been in custody since July and is on trial for allegedly leading an insurrection and abusing his power in connection with a short-lived martial law declaration in December.

On September 20, a special counsel team notified Yoon to appear for questioning next week over allegations linked to his failed martial law bid.

Special counsel Cho Eun-suk's team said it issued the summons to Yoon to appear for questioning at the Seoul High Prosecutors' Office on Wednesday.

The team is expected to question Yoon on charges of whether he incited foreign aggression by ordering a drone dispatch to Pyongyang in October, ahead of his short-lived declaration of martial law in December.

It would be the first time investigators attempt to question him over the allegation of inciting foreign aggression.

The team suspects Yoon of giving direct orders to the Drone Operations Command to dispatch drones to Pyongyang in an attempt to provoke North Korean military responses and allegedly create a pretext for the imposition of martial law.

Former drone command chief Major General Kim Yong-dae, Joint Chiefs of Staff (JCS) former Chairman Adm. Kim Myung-soo and JCS operations chief, Lt. Gen. Lee Seung-oh, have already been questioned over the allegations.

The commanders have denied any link between the drone dispatch and Yoon's martial law, arguing the operations were part of response measures to the North's balloon campaigns against the South.

However, it remains unclear whether Yoon would appear, as he has refused to cooperate with the special counsel's probe and attend his insurrection trial since July.

The team also plans to question former Defence Minister Kim Yong-hyun, who is currently in custody at the Seoul Eastern Detention Centre on charges of insurrection, officials said.

/IANS