(Bloomberg) -- Rail traffic between North Korea and Russia spiked after a summit between Kim Jong Un and Vladimir Putin, a Washington-based think tank said, citing satellite imagery.

The number of freight railcars totaled 73 on Oct. 5 at North Korea’s Tumangang rail facility, compared with the previous daily high over the past five years of 20, the Center for Strategic and International Studies said on its Beyond Parallel website. It was impossible to identify the types of cargo due to the use of tarps, it said.

The US has accused Kim of providing arms and ammunition, including shells and rockets, to aid Russia’s war in Ukraine. Pyongyang and Moscow have denied US accusations of arms transfers.

Kim spent about a week in Russia last month where he held a summit with President Putin. The North Korean leader received pledges of assistance in building satellites and firing them off on Russian rockets.

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