Some 10,000 foreigners stayed on illegally since they entered the country under a visa waiver during the Pyeongchang Winter Olympics.
Seoul permitted a visa-free, 90-day temporary stay to promote tourism during the Olympics from Feb. 9-25.
Some 351,739 foreigners took advantage of the waiver, according to a Justice Ministry report released by Liberty Korea Party lawmaker Jun Hee-kyung last week. And about 11,635 or 3.3 percent of them were still here illegally as of May 31.
They came from 135 countries, the biggest groups from Japan with 92,402, Taiwan with 54,010, Hong Kong with 39,120 and China with 38,375.
Many of the over-stayers are migrant workers who came looking for jobs or asylum seekers.
"The government failed to make any preparation for such an influx of illegal aliens when it decided to permit foreigners to enter without a visa," Jun said. "And urgent response is needed, including tracking down illegal immigrants."
