South Korean border guards arrested an American man who they believe was attempting to swim across a river into rival North Korea, a South Korean defense official said Wednesday.

The man was apprehended Tuesday night while lying on a bank of the Han River, which is in a restricted military area near the border, said the official, speaking on condition of anonymity due to office policy. The man was in his late 20s or early 30s, Yonhap news agency said, and had told investigators that he tried to go to North Korea to meet leader Kim Jong Un.

Americans are occasionally arrested after entering North Korea illegally from China but a U.S. citizen trying to get in from South Korea is unusual.

In the 1960s, several U.S. soldiers walked into the North while on a patrol near the mine-strewn Demilitarized Zone, or DMZ. Those army deserters later appeared in North Korean propaganda films and taught English.

In 1996, American Evan C. Hunziker entered the North by swimming across the Yalu River that marks the Chinese border. Hunziker, who apparently made the swim on a drunken dare, was accused of spying and detained for three months.

Hunziker, 26 at the time, was eventually freed after negotiations involving a special U.S. envoy. The North Koreans wanted to slap Hunziker with a $100,000 criminal fine but eventually agreed on a $5,000 payment to settle a bill for a hotel where he was detained. He killed himself about one month after his release.

About 27,000 North Koreans have defected to South Korea to avoid poverty and political suppression since the end of the Korean War, but some South Koreans also have attempted defect to the impoverished, authoritarian neighbor to the north. Such cases are rare.

Last year, South Korean soldiers shot and killed a man with a South Korean passport who officials said ignored warnings while swimming across the Imjin River toward North Korea.

Some recent U.S. detainees include missionaries aiming to spread the gospel in North Korea or draw attention to the country's alleged human rights abuses. On Christmas Day in 2009, Korean-American missionary Robert Park defiantly walked into the North from China calling for dismantling of the North's prison camps. Park, who was deported from the country in February 2010, has said he was tortured by interrogators.

North Korea is currently holding three Americans and the country's Supreme Court on Sunday sentenced one of them, Matthew Miller, to six years of hard labor for illegally entering the country to commit espionage. North Korea says Miller tore up his tourist visa upon arrival at Pyongyang's airport in April.

The Korean Peninsula remains in a technical state of war because the 1950-53 Korean War ended with an armistice, not a peace treaty. About 28,500 U.S. troops are stationed in South Korea to deter potential aggression from North Korea.