South Korean prosecutors are seeking a 30-year jail term for ex-president Park Geun-hye in a corruption case which led to her impeachment, the Yonhap news agency reports.

Park, 66, was dismissed in March and is standing trial on charges of bribery, abuse of power and coercion in a case that has rocked the country's business and political elite. She denies wrongdoing.

The prosecution's recommendation came two weeks after Choi Soon-sil, a longtime friend of Park who was at the centre of the scandal, was jailed for 20 years for taking bribes from "chaebol", or conglomerates, including electronics powerhouse Samsung and retail giant Lotte.

Prosecutors are also seeking a 118.5bn won ($127.1m) fine for Park, who has been detained since March 31 last year.

Park Seung-gil, a lawyer representing the former president, tearfully pleaded before Seoul Central District Court for mercy, saying Park had tried her hardest in leading the country "day and night".

Park's trial began in May and a verdict is expected before April in a case that brought scrutiny to the cosy ties between South Korea's political leaders and its largest chaebol, the so-called "Republic of Samsung".

"(Park) brought a national crisis by letting a person who has never been involved in state management rule the country," a prosecutor said.

"She and Choi took tens of billions of won in bribes and yet denied her crimes and obstructed efforts to establish the truth."

Receiving bribes carries a penalty of up to life in jail.

'Harsh sentence'

Hundreds of supporters gathered outside the court, proclaiming Park's innocence. "Immediately release our president," they chanted.

The Liberty Korea Party, a conservative opposition party formerly led by Park, condemned the call for jail.

"What the prosecution is demanding is harsher than the death penalty," the party said in a statement.

Seoul Central District Court had also sentenced Shin Dong-bin, chairman of the country's fifth-largest conglomerate, Lotte Group, to two years and six months in prison in the same case.

Seoul High Court suspended a prison sentence for Samsung Group heir Jay Y Lee in early February - a surprise decision that sent shockwaves through political and business circles.

The court sentenced Lee to two and a half years in jail on charges including bribery and embezzlement - reducing the original term by half - but suspended the sentence for four years, meaning that he is unlikely to serve any more time in jail.