A Korean-American missionary believed detained in North Korea walked into the country carrying a Bible, intent on preaching Christianity in a country that bans illegal worship _ a bold move that may put him at greater risk of harsh punishment.

Determined to bring international attention to human rights abuses in North Korea, Robert Park slipped into the communist country on Christmas Day, activists in Seoul said Thursday. The 28-year-old bore letters calling on authoritarian leader Kim Jong Il to step down and close down camps for political prisoners. He carried a Bible in one hand and the text of a hymn in the other, they said.

"I brought God's love. God loves you, and God bless you," he shouted in Korean as he crossed a frozen river dividing China from North Korea, the activists said, citing the guides who led Park to the border.

Park, of Tucson, Arizona, has not been heard from since, but one of the two guides _ both North Korean defectors _ brought back the black leather jacket, hat and gloves that Park handed over before fleeing across the border, said Jo Sung-rae of the Seoul-based group Pax Koreana.

"He asked us to give his clothes to the poor," Jo said Thursday after saying a prayer for Park at the South Korean border village of Imjingak. "I'm sure that Robert is fasting in North Korea now as he had been fasting before entering there."

North Korea announced Tuesday that an American was in custody after entering the country illegally, without identifying the person. It has said nothing more about the incident.

The detainment comes four months after two American journalists arrested at the border were freed, their 12-year sentences for illegal entry and "hostile acts" commuted after former President Bill Clinton intervened.

While Park's deliberate trip into North Korea has not garnered the same attention as the arrests of journalists Laura Ling and Euna Lee, which occurred at a time of heightened tension between North Korea and Washington, his Christian mission may raise the ire of North Korean officials, analysts said.

North Korea's criminal code punishes illegal entry with up to three years in prison, but Park could be accused of attempting to undermine the regime with Christianity, analysts said.

"Robert attempted to spread the Gospel. He planned to spread the Gospel even to North Korean soldiers if they were to arrest him" and was secretly sending Bibles to the North as well as helping North Korean citizens defect, Jo said.

North Korea's constitution guarantees freedom of religion, but in reality the government severely restricts religious observance, allowing only worship at sanctioned churches.