Outgoing United Nations Secretary General Ban Ki-moon and his wife Yoo Soon-taek unveil his official portrait at United Nations headquarters in New York City, US, December 14, 2016. [Photo/Agencies]

SEOUL - Ban Ki-moon, outgoing UN Secretary General, whose second five-year term is set to end by the end of this year, reclaimed the top spot in recent South Korean presidential polls, local survey showed on Monday.

According to a survey of 2,528 voters nationwide conducted by local pollster Realmeter between Dec. 19 and 23, support for Ban as the country's next leader was 23.3 percent, up 2.8 percentage points from the previous week.

His main support base was the North Gyeongsang province, a traditional home turf for impeached President Park Geun-hye and the ruling Saenuri Party, in which Ban garnered 35.8 percent in approval scores, up 9.3 percentage points from a week earlier.

As there is no competitive presidential contender found in the ruling bloc, Ban is seen as the last remaining hope for conservative voters.

Ban has not officially declared his run for president in his homeland, but local media outlets speculated that he had already indicated his candidacy in recent press conference with South Korean journalists in New York.

Since the scandal involving President Park erupted in late October, Ban's approval rating declined in tandem with growing fury over Park which resulted in the presidential impeachment on Dec. 9.

The outgoing UN chief was known to have been close to President Park and the ruling party, as seen in his seven meetings with Park during her four-day trip to New York in September 2015, but he recently drew a line to the close relations.

Moon Jae-in, former head of the biggest opposition Minjoo Party who had been the frontrunner in presidential surveys for the past seven weeks, surrendered to Ban last week with an approval rating of 23.1 percent. It was 0.2 percentage points lower than Ban's.

Lee Jae-myung of the Minjoo Party, mayor of Seongnam, a city to the southeast of capital Seoul, maintained the third place at 12.3 percent, but it was down 2.6 percentage points compared with a week ago.

Ahn Cheol-soo of the minor opposition People's Party came next with a support score of 8.2 percent, almost unchanged from the prior week.