By Ju-min Park SEOUL (Reuters) - North Korea has said it can detain South Korean workers at an joint industrial park in the event of a dispute with their companies, South Korea said on Tuesday, in the latest ruling that could hurt confidence in the factory complex. The Kaesong Industrial Complex is just on the North Korean side of the two Koreas' heavily defended border and is one of the few examples of cooperation between the rivals. North Korea shut down the complex for five months in 2013, during a period of diplomatic tension. South Korea has 125 companies there, most of them small- and medium-sized firms, employing 53,000 relatively cheap North Korean workers.