Two South Korean intelligence officials have been detained by Chinese authorities for 11 months for information-gathering activities related to North Korea, South Korean media reported Thursday.

According to multiple news reports, citing unnamed diplomatic sources, two agents belonging to the National Intelligence Service were arrested by Chinese Ministry of State Security last August in Shenyang in the northeastern province of Liaoning.

Since then they have been detained in Changchun, a city in the neighboring Jirin Province, and are now standing trial for spy charges.

The duo stand accused of hiring locals to collect information about the North. Liaoning and Jirin border North Korea to the south.

To win their release, the Korean government has been contacting Chinese officials, but no progress has been made so far as China refuses to release them from custody, the reports said.

Kim Sook, who was the NIS’ First Deputy Director at the time of the two’s arrest, is said to have visited the Chinese agency, asking it to deport them, but to no avail.

The NIS denied the reports.

A spokesperson for Liberty Forward Party, South Korea’s far-right minority, called on the government to step up efforts to free the two.

“This is a matter of protecting the life and safety of Korean nationals,” Rep. Lim Young-ho said.

China, North Korea’s closet ally, has been tough on South Korea’s anti-North intelligence activities on its territory.

In July 2009, a South Korean military intelligence official was released to South Korea in the form of extradition, only after serving more than a year in a Chinese jail on similar spy charges.

The Korean, surnamed Jo, was arrested by Chinese authorities for allegedly trying to get information about North Korean nuclear programs from a Chinese army official. He was sentenced to three years in prison.

By Lee Sun-young (milaya@heraldcorp.com)