SEOUL - Two American journalists sentenced in Pyongyang last week to 12 years' hard labor were detained in the Democratic People's Republic of Korea's (DPRK)  territory after crossing into the country illegally, state-run media said Tuesday, providing the first details about the circumstances of their arrest.

Laura Ling and Euna Lee of Current TV were taken into custody on the DPRK's banks of the Tumen River after crossing over illegally three months ago, the official Korean Central News Agency said.

"The accused admitted that what they did were criminal acts committed, prompted by the political motive to isolate and stifle the socialist system of the DPRK by faking up moving images aimed at falsifying its human rights performance and hurling slanders and calumnies at it," it said.

The women were detained March 17 at a time of rising tensions between DPRK and the United States over the nation's nuclear and missile programs. Weeks earlier, DPRK had announced its intention to send a satellite into space aboard a long-range rocket - a launch Washington called a cover for a test of a long-range missile designed to strike the US

DPRK went ahead with the rocket launch in early April, and conducted a nuclear test on May 25 and fired off a series of short-range missile in the days before the journalists' June 4 trial.

The women's families claim Lee, 36, and Ling, 32, had no intention of crossing into DPRK. The families have pleaded for leniency and their release on humanitarian grounds.

The details about the case involving the two women working for a San Francisco-based media venture founded by former Vice President Al Gore were released by state media just hours before President Barack Obama was to sit down at the White House with South Korean President Lee Myung-bak.

The two leaders are expected to discuss DPRK and make a strong show of unity at their summit Tuesday in Washington.