Ukraine says Russia has sent 32 tanks and 16 howitzer artillery systems across its border, threatening an already fragile ceasefire that was agreed to back in September.
"'The deployment continues of military equipment and Russian mercenaries to the front lines,' spokesman Andriy Lysenko said in a televised briefing referring to Thursday's cross-border incursion.
"The report of a new Russian movement of armor across the border follows a charge on Thursday by pro-Russian rebels in eastern Ukraine that Kiev government forces had launched a new offensive - which Kiev immediately denied."
Of course, all of this comes just days after separatists in eastern Ukraine defied the central government in Kiev by holding elections. Russia said it would recognize the results, which led to further fears from Western countries and Kiev that Russia would continue its incursion into Ukraine.
And just in case you haven't been paying attention this is a CliffNotes version of how we got here: This whole conflict started after violent protests ended in the ouster of pro-Russian President Viktor Yanukovych. Seizing on the opportunity and instability, Russia annexed Crimea, a peninsula with long, historical ties to Russia. Since then, Kiev and Russia-backed separatists have been trading words and fire. In September, they came to a cease-fire agreement.
The BBC reports that if the troop movement is confirmed, it would prove a serious blow to an already-fraying cease-fire deal. The BBC explains that earlier this week:
"President Petro Poroshenko has accused the rebels of tearing up a peace deal and said a law granting the rebel-held regions partial autonomy would be scrapped. He has ordered reinforcements to key cities in case of a rebel offensive.
"But the separatists hit back on Wednesday, arguing that it was the scrapping of the special status deal that broke the peace agreement."