Image copyright AP Image caption Protesters chanted 'Park Geun-Hye resign' as they waved candles and placards above their heads

Tens of thousands of protesters have gathered in Seoul for the fourth week in a row as they continue to demand President Park Geun-hye stand down.

The protesters chanted "Park Geun-Hye resign" as they waved candles and placards above their heads.

Ms Park is accused of allowing her friend, Choi Soon-sil, to manipulate power from behind the scenes.

The president has apologised twice on national television, but has so far resisted calls to resign.

This is despite South Korea witnessing the largest protests since pro-democracy demonstrations of the 1980s.

Organisers said as many as 500,000 people attended the candlelit rally in the capital this weekend, which brought streets to a standstill for the fourth consecutive Saturday. Police put the figure far lower.

Lee Won-cheol, a 48-year-old IT expert, told Agence France-Presse: "She is a criminal. How can we have a criminal as our president? She must step down."

Image copyright AP Image caption This is the fourth Saturday in a row people have gathered to protest

Ms Park, whose approval rating as dropped to 5%, apologised earlier this month for putting "too much faith in a personal relationship", and has pledged to co-operate in an official investigation into the scandal.

Prosecutors are expected to bring charges against Ms Choi, along with two former presidential aides, on Sunday. She was arrested earlier this month.

Ms Choi is accused of trying to extort huge sums of money from South Korean companies, and suspected of using her friendship with Ms Park to solicit business donations for a non-profit fund she controlled.