North Korean authorities have said they have arrested a US man who crossed into their territory.
The North's official KCNA news agency said the man had entered the country from China on 24 December. There is no official word on the man's identity.
However there have been reports that Robert Park, a US Christian activist, recently crossed into North Korea.
Colleagues say he wanted to highlight the country's human rights record and demand the release of prisoners.
"On December 24, a US citizen illegally entered the country across the North Korea-China border and has been detained. The person is currently undergoing questioning by a related agency," KCNA news agency said.
Associates of Mr Park reported that he had walked into North Korea from China across the frozen Tumen River on Christmas Day, 25 December.
Mr Park, a US citizen of Korean ancestry from Tucson, Arizona, claimed he had seen a vision from God of North Korea's liberation and redemption, his colleagues said.
They said he walked across the border shouting: "I am an American citizen. I brought God's love. God loves you and God bless you."
South Korean activists supporting Mr Park say he carried a letter urging the North's leader, Kim Jong-Il, to free political prisoners and improve human rights in the communist state.
Earlier this year North Korea detained two US journalists on the border with China.
Laura Ling and Euna Lee were sentenced to 12 years' hard labour but were freed as part of a diplomatic mission spearheaded by former US President Bill Clinton in August after four months in captivity.