SEOUL - South Korea's impeached President Yoon Suk-yeol appeared at a Seoul court on Thursday for the first hearing of his criminal trial over insurrection charges, during which his lawyers demanded his release from jail.

TV footage aired by local broadcasters showed justice ministry vehicles leaving the Seoul Detention Centre where Yoon is being held before arriving at the court where lines of police buses were parked outside to ensure security.

The court heard a bid by Yoon's lawyers to cancel his detention as they argued that the insurrection probe had been conducted in an illegal manner, and that there was no risk of Yoon trying to destroy evidence.

Prosecutors last month indicted Yoon after accusing him of leading an insurrection with his short-lived imposition of martial law on December 3.

The charges are unprecedented for a sitting South Korean president, and if convicted, Yoon could face years in prison for his martial law decree, which shocked the country and sought to ban political and parliamentary activity and control the media.

His move set off a wave of political upheaval in Asia's fourth-largest economy and a top US ally, with the prime minister also impeached and suspended from power and a number of top military officials indicted for their roles in the alleged insurrection.

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Prosecutors on Thursday called for quick proceedings considering the case's "gravity", but Yoon's lawyers said they needed more time to review records.

Yoon had "no intention to paralyse the country," one of his lawyers told the court, adding that his martial law declaration was to inform the public of the "legislative dictatorship of the huge opposition party".

A judge said the court would hold the next hearing on the criminal case on March 24.

Yoon is also facing a parallel impeachment trial conducted by the Constitutional Court which has entered its final phase.

The top court will hear witnesses testify, including Prime Minister Han Duck-soo later on Thursday. Yoon will also attend the impeachment trial hearing, according to media reports.

The Constitutional Court is reviewing parliament's impeachment of Yoon on December 14 and will decide whether to remove him from office permanently or reinstate him.

Yoon and his lawyers have argued that he never intended to fully impose martial law but had only meant the measures as a warning to break a political deadlock.

If Yoon is removed, a new presidential election must be held within 60 days.