Four in 10 foreigners who illegally stayed in South Korea last year entered the country without visas and stayed beyond the visa-free period, data from the justice ministry showed Saturday.

The number of illegal aliens in South Korea came to 423,675 as of the end of last year, accounting for 16.9 percent of the total foreigners staying in the nation, according to the data cited by Rep. Song Seong-jun of the ruling People Power Party.

Of the illegal aliens, the number of those who arrived in South Korea with a visa waiver came to 169,000, the largest proportion at 40 percent, followed by those with a short-term stay visa at 87,000, or 20.5 percent.

Such foreigners are believed to be illegally staying in South Korea to engage in economic activities without proper employment visas.

By nationality, the number of Thais who illegally stayed in South Korea reached 145,000, the largest share of 76.3 percent, followed by Chinese with 15,000 and people from Kazakhstan with 11,000, the data showed.

The South Korean government suspended visa waiver programs with Pakistan in 2001 and Bangladesh in 2008, citing a sharp rise in illegal aliens from those nations. (Yonhap)