Russia is buying large quantities of ammunition from North Korea to replenish stocks depleted by months of intense fighting in Ukraine, a US official said Tuesday.

Russia invaded Ukraine on February 24 with apparent expectations of taking control of the country within weeks.

But Ukraine has halted the advance with the help of arms and ammunition from the United States and other NATO and European allies.

“The Russian Defense Ministry is in the process of buying millions of missiles and artillery shells from North Korea for use on the battlefield in Ukraine,” a US official said in a statement.

“This purchase indicates that the Russian military continues to suffer from severe supply shortages in Ukraine, due in part to export controls and sanctions,” the official said, for the sake of anonymity.

Both warring parties used huge amounts of artillery ammunition and lost large amounts of armor in the grueling battle.

But western sanctions have made it difficult for Moscow to acquire components to make spare parts, including computer chips.

Under that pressure, the US official said, “We understand that Russia may seek to purchase additional North Korean military equipment in the future.”