(Reuters) -- A U.S. citizen who illegally entered North Korea delivered a lengthy denunciation of U.S. domestic and foreign policy Sunday and said he was seeking political asylum in Venezuela, North Korean official media said.

The man identified himself as Arturo Pierre Martinez, 29, of El Paso, Texas, in video footage of a press conference released by the KCNA news agency and said he had taken "a risky journey to reach [North Korea] so that I could pass along some very valuable and disturbing information."

Martinez spoke of human-rights violations committed by the U.S. government and its attempt at forcing imperialist influence and domination on other countries, KCNA said in an article released with the footage.

Reclusive and impoverished North Korea is under international sanctions for its nuclear and missile programs. It regularly threatens war on democratic South Korea and its major ally, the U.S.

Martinez's mother told CNN her son was mentally unstable and has bipolar disorder, and had previously tried to enter North Korea from South Korea by swimming across a river. He was captured and sent back to the U.S., where he was committed to a psychiatric hospital in California, she said, according to CNN.

"He is very smart and he got the court to let him out and instead of coming home to us, he bought a ticket and left for China," the television news channel quoted Patricia Eugenia Martinez as saying.

In September, South Korean media reported that a man in his late 20s had been arrested by its marines for swimming in a river that flows toward North Korea. The man had been trying to go there to meet its leader, local media reported at the time.

Martinez said in the KCNA article that he had been staying in a nice hotel and was being treated well by the North Korean government and that he would seek political asylum in Venezuela.

Martinez said he chose to come to North Korea to talk about U.S. policy because it has successfully defied U.S. influence by maintaining a "very powerful military."

It was not immediately clear how Martinez entered North Korea. CNN cited a North Korean statement as saying Martinez entered the country two days after U.S. intelligence chief James Clapper arrived in Pyongyang to negotiate the release of detained Americans Matthew Miller and Kenneth Bae.

Miller and Bae had both been serving hard labor sentences in North Korea for breaking local laws, but were released in November during Clapper's visit. A third detained U.S. citizen, Jeffrey Fowle, was released in October.

"[I am] extremely grateful for having been pardoned from the punishments given to violators of these laws, and for the most generous reception I have received," CNN reported Martinez as saying in a statement at the news conference.

Venezuelan President Nicolas Maduro has railed against the U.S. Senate for passing a bill that would impose sanctions on government officials found to have violated protesters' rights during demonstrations this year.

Critics of Maduro have said he blasts the U.S. to distract Venezuelans from the cash-strapped country's ballooning economic crisis.

(Reporting by James Pearson and Kahyun Yang; Editing by Simon Cameron-Moore, Jack Kim and Nick Macfie)