Fresh Russian military equipment has been seen coming into Ukraine from Russia in the past 24 hours, Ukrainian military spokesperson said.
The equipment reportedly included three Grad missile system.
Russian drones had violated Ukrainian air space on 10 occasions, the spokesperson said.
Ukrainian rebels said earlier they were receiving new armoured vehicles and fighters trained in Russia. A separatist leader said in a video statement they plan to launch a major counter-offensive against government forces.
Russia has previously denied arming the rebels.