Former head of the main opposition party in South Korea widened his lead in a recent presidential poll over former UN chief who returned back to his home country about 10 days ago.

Moon Jae-in, former Minjoo Party chief, gained 29.1 percent in approval rating as next president, according to a Realmeter survey released on Monday. It was up 3.0 percentage points from the previous week.

Support for Moon came closer to 30 percent, strengthening his lead over former UN chief Ban Ki-moon who won 19.8 percent last week, down 2.4 percentage points from a week ago.

Ban, who arrived in South Korea on Jan. 12 after his second five-year term in the top UN post ended at the end of last year, saw public support for him improved in the first week of his return.

The career diplomat has never officially declared his run for presidency, but he has been viewed as the best hope in the conservative camp as the impeachment of President Park pulled down support for conservative politicians.

However, his so-called "people-friendly" moves raised doubts about qualification as next president, divulging his nervous response to negative comments or questions toward him.

Local news media speculations are being centered on fraud cases filed in a U.S. court against Ban's brother and nephew, while some speculated Ban received kickbacks from a South Korean business tycoon.

Lee Jae-myung, mayor of Seongnam city to the southeast of Seoul who is affiliated with the Minjoo Party, won an approval rating of 10.1 percent. He officially declared his run for president on Monday.

Ahn Cheol-soo, former co-chairman of the minor opposition People's Party, a splinter from the Minjoo Party, saw his support rise from 7.0 percent to 7.4 percent last week.

source: Xinhua