South Korean Prime Minister and the acting President Hwang Kyo-ahn releases a statement to the nation at the Goverment Complex in Seoul, South Korea, December 9, 2016. REUTERS/Kim Hong-Ji

South Korea’s prime minister sought to calm anxiety over national security and to reassure financial markets on Saturday, a day after parliament voted to impeach President Park Geun-hye, making him acting leader.

Prime Minister Hwang Kyo-ahn, who assumed presidential authority late on Friday after the overwhelming impeachment vote, and with more protests against Park due later on Saturday, called on authorities to ensure that rallies are peaceful.

"So far, financial and foreign exchange markets have been relatively stable and there are no signs of unusual movements by the North, but all public servants should bear vigilance in mind as they conduct their duties," Hwang told a meeting.

He said national security was the priority and reiterated that the military should be on high alert for any provocation by old rival North Korea, including the possibility of cyber attacks aimed at sowing confusion in the South.

Park’s powers were suspended after 234 of parliament’s 300 members voted to impeach her, meaning more than 60 members of her own party backed the motion against her.

The impeachment, which has to be reviewed and approved by a nine-judge Constitutional Court within 180 days to remove Park from office, sets the stage for her to become the country’s first elected leader to be ousted in disgrace.

Park, 64, the daughter of a former military ruler, is accused of colluding with a friend and a former aide, both of whom prosecutors have indicted, to pressure big businesses to donate to foundations set up to back her policy initiatives.

Park, who is serving a single five-year term ending in February 2018, has denied wrongdoing but apologised for carelessness in her ties with her friend, Choi Soon-sil.

For six consecutive Saturdays, huge crowds have gathered in central Seoul in peaceful demonstrations calling for Park to step down, with another planned for Saturday.

"The candle-lit rallies we have been holding and the weekend rally in Kwanghwamun will go on," organisers said in a statement, referring to an imposing gate that opens to an imperial palace in front of the presidential Blue House, where Park remains despite losing her powers.

"The impeachment is the start, not the end," they said.

If Park leaves office early, an election must be held within 60 days. She would also lose presidential immunity from prosecution. Prosecutors have named Park as an accomplice in their investigation.

Earlier, the Bank of Korea said the financial market impact of the impeachment appeared to be limited after a meeting to review policy measures that it may take. Governor Lee Ju-yeol asked for close monitoring of the markets.

The United States, which has about 28,500 troops stationed in South Korea, was in close contact with South Korea and remained a strong ally, the White House said late on Friday.

(Editing by Tony Munroe, Robert Birsel)