Among foreign nationals in South Korea, approximately 1 in 6 -- 15.8 percent -- is here illegally, according to government data from the end of June.

Out of the country's total foreign population of 2.61 million -- including tourists and other nonresidents --- 414,730 are in the country without permission, according to Justice Ministry statistics for June.

That is down from the record high of 430,389 in October last year. The proportion is also down from 20 percent at the end of 2021, as the return of tourists after pandemic measures were lifted rose the overall number of foreign nationals here. July figures released by the Korea Immigration Service showed a continued decrease, to 412,594.

This comes after a long-term upward trend. The number of foreign nationals here without valid visas rose sharply from just under 209,000 at the end of 2016 to over 390,000 at the end of 2019. The increase has slowed since then, but officials have struggled to bring the number down.

Among the 414,730 unregistered foreign nationals, the largest group -- comprising 38.4 percent or 159,283 people -- were "visa-exempt" visitors who exceeded the permitted length of their stay here. Following them were 87,067 people who overstayed more formal tourist visas, typically issued for stays of less than 90 days.

By nationality, Thais made up the largest portion of unregistered foreign residents in 2023, with 152,265 people, representing 35.9 percent of the total. Vietnamese followed at 18.9 percent, Chinese at 15.2 percent, Mongolians at 4.4 percent, and Filipinos and Kazakhstan nationals at 3.3 percent each.

In June, ruling People Power Party Rep. Kim Mi-ae released data from the Korean National Police Agency saying that of the 549 foreign nationals investigated for drug offenses from January to May this year, 317 were in the country illegally. The number of unregistered foreign nationals arrested for drug offenses has risen from 172 cases in 2018 to 1,083 in 2023.

The Ministry of Justice also stated that a record high of 23,724 people were caught violating immigration rules during a crackdown in the first half of this year. Additionally, the Ministry noted that another 20,523 foreign residents voluntarily left Korea during the same period after staying here illegally.

Announcing these figures at a press briefing in July, Justice Minister Park Sung-jae stressed the Ministry's commitment to maintaining stringent immigration controls, with plans to reduce the number of foreign residents without a visa from the current 414,730 people to 200,000 by 2027 through intensified crackdowns.