Russia has fired North Korean-supplied short-range ballistic missiles into Ukraine twice in the past week, an “escalation” of Pyongyang’s support for Moscow that has serious implications for both the war in Europe and security on the Korean Peninsula, the White House said Thursday.

The North Korean-made missiles were fired at Ukraine on December 30 and January 2, National Security Council spokesperson John Kirby said at a White House briefing. They were among at least 500 missiles and drones fired at Ukraine around the New Year’s holiday, according to Kyiv.

The December 30 attack involved a lone missile that fell into a field, while Russia’s January 2 assault involved multiple missiles, he said. The impacts of missiles fired on January 2 are still being assessed, Kirby said, adding they were part of a “massive” Russian assault.