The U.S. State Department on Tuesday warned U.S. citizens against entering the Democratic People's Republic of Korea (DPRK) without permission from the east Asian country.

"While the United States government does not restrict travel to North Korea, the Department of State warns U.S. citizens against entering North Korea without first having received an explicit official permission and an entry visa from the Government of North Korea (Democratic People's Republic of Korea)," said the State Department in a statement.

The department said that U.S. citizens crossing into DPRK "without proper documentation" have been subject to arrest and long-term detention.

The United States does not have diplomatic or consular relations with DPRK. A number of American citizens were detained by DPRK for illegal entry in the past.

Mahli Gomes, a 30-year-old from Boston who once taught English in South Korea, was detained by the DPRK on Jan. 25 for illegal entry into the country.

In August, former U.S. President Jimmy Carter flew to DPRK on a private trip, bringing Gomes back to the United States.

In a similar visit to DPRK in August 2009, former U.S. President Bill Clinton secured the release of two female U.S. journalists detained there for illegal entry.