(VOVworld) - Ukraine warned Thursday that the security situation in rebel-held areas in the east has worsened steadily as separatist fighters move closer to demarcation lines separating them from government forces.

Unmarked military vehicles parked on a road outside the separatist rebel-held eastern Ukrainian town of Snizhne, 80 km  from Donetsk on Saturday Nov. 8, 2014. (AP Photo/Mstyslav Chernov)

National Security and Defence Council spokesman Andriy Lysenko said that the Russian army is massing troops, including air defence units, near the border.

Lysenko’s warnings of possible renewed combat follow recent observations of large military convoys on the move around separatist-controlled areas. Trucks transporting troops, ammunition, fuel and heavy artillery have been seen travelling primarily in the direction of Donetsk, the main rebel city.

Ukraine accuses Russia of directly supplying separatist forces, but Russia has repeatedly denied that charge.