SEOUL (AFP) - North Korea said Tuesday it has detained an American for illegal entry, its first apparent reference to a Christian activist who crossed into the communist state on a lone rights crusade. An American was detained after illegally entering the DPRK (North Korea) through the DPRK-China border on December 24, Pyongyangs Korean Central News Agency said in a one-paragraph report. He is now under investigation by a relevant organ. Robert Park, 28, was reported by colleagues to have crossed the frozen Tumen River from China in a one-man protest against repression in the hardline North. A US citizen of Korean ancestry, he claimed he had seen a vision from God of North Koreas liberation and redemption, his colleagues said, adding that Park crossed the border shouting, I came here to proclaim Gods love. Park carried a letter calling on North Korean leader Kim Jong-Il to release political prisoners, shut concentration camps and take steps to improve rights and conditions, his colleagues said. The US State Department expressed concern Monday the North may have detained the activist from Tucson in Arizona. It said Sweden, which represents US interests in Pyongyang in the absence of diplomatic relations, has offered to seek more information. Cho Sung-Rae, one of Parks fellow activists in Seoul, said Park was detained on Christmas Day and not December 24. I dont understand why North Korea is trying to distort facts, Cho told AFP. Maybe it could be part of its attempt to avoid criticism that he was detained on Christmas Day. Cho urged Pyongyang immediately to release Park and said the US government should intervene, even though Park has said he would not seek such intervention.