*

Constitutional Court starts review of Yoon's impeachment

*

First public hearing will be held on Dec. 27

*

Investigators plan to question Yoon this week

*

Financial markets stabilise

(Updates with court's first hearing in paragraph 2-3, foreign

minister in paragraph 16)

By Joyce Lee and Ju-min Park

SEOUL, Dec 16 (Reuters) - South Korea's Constitutional

Court on Monday began reviewing the impeachment of President

Yoon Suk Yeol over his Dec. 3 martial law attempt, starting a

process to decide if he will be removed from office, while

investigators plan to question him this week.

The court will hold the first public hearing on Dec. 27,

spokesperson Lee Jean told a news conference, after the court's

six justices met to discuss plans for reviewing the impeachment

by the opposition-controlled parliament on Saturday.

The court has up to six months to decide whether to remove

Yoon from office or to reinstate him. The first hearing will be

"preparatory" to confirm major legal issues of the case and

schedule among other matters, Lee said.

Yoon is not required to attend that hearing, he said.

In 2017, the court took three months to issue a ruling to

strip then-President Park Geun-hye's presidency following her

impeachment for abusing the powers of her office.

Yoon and a number of senior officials face potential charges

of insurrection, for the short-lived martial law.

A joint team of investigators from the police, the defence

ministry and an anti-corruption agency are planning to call Yoon

in for questioning at 10 a.m. (0100 GMT) on Wednesday, a police

official told Reuters.

Investigators tried to serve a summon for Yoon to appear by

delivering it to the presidential office and his official

residence, but the presidential security service declined to

receive it saying it was not in the position to do so, Yonhap

news said.

On Sunday Yoon did not appear in response to a summons for

questioning by a separate investigation by the prosecutors'

office, Yonhap news reported. Yoon cited he was still forming a

legal team for his defence as the reason, it said.

The government led by acting president, Han Duck-soo, was

moving quickly to reassure international partners and calm

financial markets, while the main opposition party pledged to

cooperate in efforts to stabilize the situation.

Early on Monday, the finance minister, Bank of Korea

governor and top financial regulators met and pledged

around-the-clock monitoring of financial and foreign exchange

markets.

The benchmark KOSPI index rose for a fifth straight

session on Monday and traded at its highest levels in more than

two weeks, as authorities vowed to stabilize financial markets

and analysts noted eased political uncertainty.

Yoon's surprise martial law declaration and the ensuing

political crisis spooked markets and South Korea's diplomatic

partners, worried over the country's ability to deter

nuclear-armed North Korea.

In one of his first moves as acting president, Han spoke

with U.S. President Joe Biden by telephone on Sunday, pledging

unwavering commitment to pursue foreign and security policies

based on the alliance between the two countries.

Opposition Democratic Party leader Lee Jae-myung welcomed

U.S. President-elect Donald Trump's selection of his former

intelligence chief to handle special missions including North

Korea as a sign of commitment for dialogue to ease tensions.

Foreign Minister Cho Tae-yul said the nomination of Richard

Grenell indicated North Korea will be one of the top priorities

of Trump's presidency. Trump met North Korean leader Kim Jong Un

on three occasions during his first term.

The Saturday impeachment vote passed with at least 12

members of Yoon's ruling People Power Party joining in favour,

which has thrown the party into a disarray with its leader Han

Dong-hoon announcing his resignation on Monday.