Ukraine has accused Russia of another military incursion into the separatist region of Luhansk, raising tensions between the two nations that could threaten the Minsk cease-fire signed in September.

Ukrainian military officers reported that 32 Russian tanks crossed into the separatist region of Luhansk on Thursday along with 16 howitzers and 30 trucks with Russian troops, reported the Telegraph. Another column of trucks, including three mobile radar units, crossed as well through the border town of Izvaryne.

"Supplies of military equipment and enemy fighters from the Russian Federation are continuing," military spokesman Andriy Lysenko said during a press briefing in Kiev, according to Reuters. He added that five Ukrainian soldiers had been killed in the last 24 hours.

Though NATO did not provide any substantiation of Russian incursion into the Ukraine, it said it had monitored increasing activity along the border and has evidence that Russia has supported the rebels before.

"If this crossing into Ukraine is confirmed it would be further evidence of Russia's aggression and direct involvement in destabilizing Ukraine," a NATO officer said. Russia has not answered to the recent allegations but stated its continued support for the ceasefire.

"We support the continuation of the Minsk process and advocate holding another meeting of the Contact Group (of negotiators)," Kremlin foreign policy adviser Yuri Ushakov said. "But not everything depends on us. There are a lot of factors."

This aggression comes only a week after elections in the two separatist regions re-elected pro-Russia leaders. However, neither Ukraine nor its allies recognize the results and, instead, view it as a provocation and violation of the cease-fire signed in Minsk.

"The elected representatives of Donetsk and Luhansk regions obtained a mandate to hold negotiations with central Ukrainian authorities to solve problems ... via a political dialogue," said Georgy Karasin, Russia's deputy foreign minister, after the elections, reports the Guardian.

The reports of military movements within the separatist regions, however, could damage any political dialogue and may be seen by some as a belligerent move.