Arrested ex-South Korean president's supporters stage rally in Seoul
Supporters of arrested former president Park Geun-hye have begun rallying in South Korea's capital to call for her release.
Thousands are expected at the protest near Seoul's City Hall, and more than 10,000 officers are being deployed amid concerns there may be clashes.
Opponents and supporters of Park have filled the capital's streets with passionate rallies in recent months, reflecting the country's deep divide on the issue.
Park was jailed on Friday over allegations that she colluded with a confidante, Choi Soon-sil, to extort money from businesses, take bribes and allow Choi to unlawfully interfere with state affairs.
The Constitutional Court ruled on March 10 to remove her from office after she was impeached in December.
Park's opponents held their own protests in nearby streets, celebrating her arrest and calling for her conservative policies to be erased.
Seoul police used thousands of police officers and hundreds of buses to separate the two crowds.
Park's arrest marked a stunning fall for South Korea's first woman president, who convincingly defeated her liberal opponent in 2012 thanks to overwhelming support from conservative older voters, who remembered her dictator father, Park Chung-hee, as a hero who rebuilt a nation devastated by the 1950-53 war with North Korea.
Gathering in streets near Seoul City Hall, Park's supporters, many of them in their sixties or older, chanted: "Release President Park Geun-hye" and "Disband the National Assembly".
They roared approval as organisers accused Park's political rivals of being "leftist North Korea sympathisers" and "turncoats".
Jung Mi-hong, one of the organisers, told the crowd: "She could have avoided this all if she wanted to, but Park chose the road of a martyr.
"She has offered to sacrifice herself to protect the constitutionalism of the Republic of Korea and a free democracy."
Chung Kwang-taek, a protester, said that Park's opponents "ruthlessly attacked a lonely woman who dedicated herself to the country" and that she would overcome her troubles to "live forever as a historical figure".
Prosecutors can detain Park for up to 20 days, during which time they are expected to formally charge her.
The most damning accusation alleges that Park took tens of millions of dollars in bribes from technology giant Samsung in exchange for business favours, which would be punishable by a prison term longer than 10 years and even a life sentence if she is convicted.
Park has apologised for putting trust in her jailed friend, Choi, but has denied breaking any laws.