The number of South Korean visitors to North Korea through a western border immigration office topped 1 million on Wednesday, nine years and three months after its opening, the Unification Ministry said Wednesday.

South Korea opened the immigration control office at Dorasan Station, the country's northernmost train station, 60 kilometers north of Seoul, in 2003 for its people who travel to North Korea's western border city of Kaesong for business or tourism.

Inter-Korean cooperation and exchanges increased sharply following a landmark inter-Korean summit in 2000. About 400 South Koreans head to Kaesong a day on average mostly to visit the Kaesong Industrial Complex, according to the ministry, which handles inter-Korean affairs.

On Wednesday, Kang Mi-hwa, a female official of footwear manufacturer Samduk Tongsang Co., became the 1 millionth person to have passed through the office.

Kang, who has traveled to and from the South-North industrial complex in Kaesong since 2005, said she was "honored" to be the 1 millionth person to make the crossing.

She also said that North Korean workers wear more colorful clothes in recent years and that South and North Korean workers do not feel any sense of difference as they work together in the factory park.

The complex, which combines South Korea's capital and technology with the North's cheap labor, has become the last-remaining symbol of inter-Korean economic cooperation amid lingering tensions following the North's two deadly attacks on the South in 2010.

Currently, more than 120 South Korean companies employ more than 50,000 North Korean workers to produce kitchenware, watches, shoes and other labor-intensive goods.

South Korea suspended a tour program to Kaesong in 2008 following the shooting death of a South Korean tourist by a North Korean soldier near a North Korean mountain resort on the east coast.

Kaesong served as the capital for most of the Goryeo Dynasty, that ruled the Korean Peninsula from 918 to 1392. (Yonhap)