Senior politicians and military leaders from around the world will meet in Germany on Friday with Ukrainian officials expected to address the security conference as they try to fend off Russian missile strikes on cities and massed assaults on front lines.

Bolstered by tens of thousands of reservists, Russia has intensified ground attacks across southern and eastern Ukraine, and, as the first anniversary of its Feb. 24 invasion nears, a major new Russian offensive appears to be taking shape.

Russia rained missiles across Ukraine on Thursday and struck its largest oil refinery. Of at least 36 missiles that Russia fired about 16 were shot down, the air force said, a lower rate than normal.