A group of South Korean firms involved in now-suspended inter-Korean economic cooperation called on the government Friday to lift sanctions on North Korea and restart a tour program to Mount Kumgang on the communist nation's southeast coast.

Representatives from the embattled companies claimed that South Korea has suffered a total of 15.8 trillion won (US$14 billion) in economic loss over the past four years due to the so-called May 24th Measures, as they held a joint rally with some progressive activists at Gwanghwamun Square in central Seoul.

The sanctions, imposed on the North for its deadly torpedo attack on a South Korean warship in 2010, have effectively suspended all inter-Korean economic projects except for the jointly operated Kaesong Industrial Complex.

They claimed that the government has given "special favors" to three major South Korean firms pushing for a joint logistics project with North Korea and Russia.   

POSCO is seeking to bring in Russian coal through the North's port of Rajin via the Russian city of Khasan. It has teamed up with Hyundai Merchant Marine Co. and Korail Corp. for the envisioned project supported by the Park Geun-hye administration.

The first test run was carried out earlier this month and the South's consortium is expected to sign a formal contract next year.

"The government should first remove the sanctions blocking South-North exchanges and cooperation," they said in a statement.

South Korean government officials acknowledge that the May 24th Measures is one of the biggest obstacles against efforts to improve ties with Pyongyang.

But they remain adamant that the North should offer an apology for the naval attack that killed 46 South Korean sailors. The North has denied responsibility. (Yonhap)