A group of South Korean firms is seeking North Korea's approval for another shipment of Russian coal through North Korea in late April, a source said Tuesday.

It would be the second of its kind involving the two Koreas and Russia.

In November, 40,500 tons of Russian coal arrived in South Korea on a ship from the North Korean port city of Rajin after being transported from Russia's border city of Khasan on a re-connected railway in the first pilot program for the so-called Rajin-Khasan logistics project.

A group of three South Korean firms has been in talks with North Korea and Russia over another pilot operation, during which some 150,000 tons of Russian coal may be shipped to the South between late April and early May, according to the source.

"As North Korea has not given final approval for the second operation, the date and size of the shipment has not been decided," the source said, requesting anonymity.

The logistics project is seen as a symbol of trilateral cooperation between the two Koreas and Russia at a time when inter-Korean relations remain stagnant.

The project involves three South Korean firms -- top steelmaker POSCO, shipper Hyundai Merchant Marine Co. and state train operator Korail Corp. They will decide on whether to clinch a formal contract based on the outcome of the two pilot operations.

The project could help realize South Korean President Park Geun-hye's vision for a united Eurasia.

In October 2013, Park unveiled her Eurasia initiative that calls for, among other things, infrastructure development and freer trade among Eurasian nations by linking their railways.

South Korea imposed the May 24 punitive sanctions on North Korea in 2010 following Pyongyang's deadly sinking of the Cheonan warship in March of that year.

The move has suspended all trade and exchange programs with the North, apart from a joint factory park project in the North Korean border city of Kaesong. The three-way logistics project also has been regarded as an exception. (Yonhap)