The state Korean Central News Agency said authorities were investigating him for committing acts inconsistent with the purpose of a tourist visit. It did not give details.
"American citizen Jeffrey Edward Fowle entered the DPRK as a tourist on April 29 and acted in violation of the DPRK law, contrary to the purpose of tourism during his stay," KCNA reported, referring to the country's official name, the Democratic People's Republic of Korea.
The U.S. State Department confirmed an American was detained, but did not identify the person or provide details for privacy reasons.
"We are aware that a U.S. citizen has been detained in North Korea. This is the third U.S. citizen that has been detained in North Korea," spokeswoman Marie Harf told reporters in Washington. She added there's "no greater priority for us than the welfare and safety of U.S. citizens abroad."
Harf did not say whether Sweden, which that handles consular matters for Americans in North Korea, had been granted access to the American. She said the department has a warning against travel to North Korea and that being part of a tour group will not prevent a possible arrest.
A 24-year-old American man was detained in April for alleged improper behavior while entering the country. The tourist agency he traveled with identified him as Matthew Miller. North Korea said he entered the country on April 10 with a tourist visa, but tore it up and shouted that he wanted to seek asylum. The brief report said he chose the North "as a shelter."
North Korea also has been holding a Korean-American missionary, Kenneth Bae, since November 2012. Bae was sentenced to 15 years of hard labor for what the North says were hostile acts against the state.
North Korea has been pushing to promote tourism as part of efforts to earn badly needed foreign currency, but the country is also extremely sensitive about how visitors act while in the country.
Friday's announcement came as tension on the Korean Peninsula remains high with North Korea keeping up rhetoric against the U.S. and South Korea following its series of missile and rocket launches earlier this year. The North's state media have also unleashed racist and sexist slurs against U.S. and South Korean leaders.
The peninsula is still 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.
The U.S. and North Korea do not have diplomatic relations so Sweden, which has an embassy in Pyongyang, oversees consular issues for the United States there. Unless a detainee signs a privacy waiver, the State Department cannot give details about the case.
In March, North Korea deported an Australian missionary detained for spreading Christianity in the country after he apologized for anti-state religious acts and requested forgiveness.
In December, North Korea released 85-year-old American veteran of the Korean War, Merrill Newman, who was held for several weeks after traveling to North Korea as a tourist. Newman was freed after he gave a videotaped confession in which he apologized for killing North Koreans during the war. Newman later said the confession was given involuntarily and under duress.
Associated Press writer Matthew Pennington in Washington contributed to this report.