Seoul - Two US reporters detained by North Korean border guards might be charged with espionage, a South Korean newspaper reported Tuesday.

The two women were taken to the North Korean capital, Pyongyang, for questioning a day after their March 17 arrests on the Chinese-North Korean border, YoongAng Ilbo reported.

Unnamed South Korean sources told the newspaper that Korean-American Euna Lee and Chinese-American Laura Ling might be charged with espionage because they crossed the border at the Tumen River. Such an offense carries a minimum sentence of 20 years in prison.

Lee and Ling were collecting information on North Koreans fleeing their country and were visiting a spot on the border where many refugees flee to China.

Stalinist North Korea confirmed the journalists' arrests Saturday and said they were accused of illegal border crossing, according to state-controlled media.

South Korean reports said the two employees of US-based Current TV, co-founded by Nobel peace laureate and former US vice president Al Gore, were taken by North Korean soldiers as they were filming the North Korean side of the border.

The press-freedom organization Reporters Without Borders called for North Korea to release the two journalists.

"We want to launch a form of appeal for their unconditional and immediate release," spokesman Vincent Brossel was quoted as saying by South Korea's Yonhap News Agency. "They were covering a very important issue, the issue of North Korean refugees at the Chinese border."

Brossel called on China to investigate the arrests to determine what side of the border they occurred upon.

The United States has also been working for Lee and Ling's release. However, it and North Korea have no formal diplomatic ties but communicate through the Swedish embassy in Pyongyang and the United Nations in New York. (dpa)