KYIV — Russia rained missiles across Ukraine on Thursday and struck its largest oil refinery, Kyiv said, while the head of the Wagner mercenary group predicted the long-besieged city of Bakhmut would fall within a couple of months.

Following a pattern of heavy bombardments after Ukrainian battlefield or diplomatic gains, Russia launched 36 missiles in the early hours, Ukraine’s Air Force said, after NATO alliance officials met the previous day to plot more support for Kyiv.