SEOUL, Sept. 7 (Xinhua) -- South Korean President Moon Jae-in's approval rating fell below 70 percent for the first time since his inauguration in early May on geopolitical risks caused by the Democratic People's Republic of Korea (DPRK)'s sixth nuclear test.

According to the Realmater survey released Thursday, Moon gained 69 percent of support this week, down 4.1 percentage points from the previous week.

It was based on a survey of 1,528 voters conducted from Monday to Wednesday. It had 2.5 percentage points in margin of error with a 95 percent confidence level.

It marked the first time since Moon took office on May 10 that his support scores fell below 70 percent.

The lower approval rating was attributed to the rising geopolitical risks on the Korean Peninsula, which was caused by the DPRK's test on Sunday of what it claimed was a hydrogen bomb warhead that can be loaded onto a ballistic missile with intercontinental capability.

The daily support for Moon continued to decline from 70.8 percent Monday to 68.1 percent Wednesday.

The pollster said the DPRK's sixth nuclear test increased worry about the security crisis, leading to lower support for Moon.

Moon's ruling Democratic Party kept the top post with 50.7 percent of support, but it was down 0.6 percentage points from the prior week.

The main opposition Liberty Korea Party won 15.5 percent in approval rating, down 0.9 percentage points from a week earlier.

The minor conservative Righteous Party and the centrist People's Party gained 6.3 percent and 6 percent respectively. The minor progressive Justice Party garnered 5.4 percent in support scores.