Supporters of arrested former President Park Geun-hye have begun rallying in South Korea's capital for her release.

Thousands were expected at Saturday's protest near Seoul's City Hall, and more than 10,000 officers were being deployed amid concerns of clashes.

Opponents and supporters of Park have filled the capital's streets with passionate rallies in recent months, reflecting the country's deep divide.

Park was jailed Friday over allegations that she colluded with a confidante to extort money from businesses, take bribes and allow the friend to unlawfully interfere with state affairs.

The Constitutional Court ruled March 10 to remove her from office after she was impeached in December. (AP)