North Korea’s munitions factories are “operating at full capacity” to produce weapons and shells for Russia, according to South Korea’s defense minister, as Moscow’s devastating war in Ukraine grinds into a third year.

The latest estimate from South Korea offers fresh clues on the crucial but highly secretive role North Korea is playing to help resupply Moscow’s war of attrition at a time when Ukraine’s own need for vital military resupplies is being held up by predominantly Republican lawmakers in Washington.

The weapons and military equipment, which include millions of rounds of artillery shells, is being delivered to Russia in exchange for shipments of food and other necessities, South Korean Defense Minister Shin Won-sik said Monday.

Since August, Pyongyang has shipped about 6,700 containers to Russia, which could accommodate more than 3 million rounds of 152 mm artillery shells or more than 500,000 rounds of 122 mm multiple rocket launchers, according to Shin’s ministry.