Two South Korean men have been indicted on charges of contacting North Korean agents and producing reports to send information on domestic affairs to Pyongyang, prosecutors said Tuesday.

The Seoul Central District Prosecutors' Office said the suspects, identified only by their surnames Lee and Kim, are accused of meeting with North Korean intelligence agents in Vietnam in March 2014 and August 2015 and returning home with instructions.

They allegedly made reports on South Korea's key affairs and wrote letters praising Kim Jong-un and the regime's former leaders between December 2014 and April 2015.

Still, prosecutors said it is unclear whether the reports and letters were actually sent to Pyongyang.

Under the National Security Law, South Korean citizens are prohibited from contacting North Koreans without government approval or engaging in activities benefiting the North.

The two suspects have been refusing to make a statement during the investigation, according to prosecutors.

Prosecutors said they need to further analyze the confiscated articles to decide whether the suspects can be charged with espionage activities.

Earlier this month, South Korea's spy agency revealed camera footage of its agents arresting Kim, 52, at a PC cafe in southern Seoul at the parliament's intelligence committee.

He was previously known to be a pastor who impersonated a human rights activist, but prosecutors said both suspects do not seem to hold regular jobs. (Yonhap)