Ukraine's President Petro Poroshenko warned the country's military to be ready for a "full-scale invasion" by Russian forces amid stepped up fighting near the border that has occurred despite a cease-fire agreement.

Poroshenko said 9,000 Russian troops were in Ukrainian territory already, a charge Moscow has denied. On Wednesday, west of the city of Donetsk, there was a 12-hour tank and artillery duel between Ukrainian forces and Russian-backed separatists — some of the fiercest fighting since a temporary truce went into effect in February.

"There is a colossal threat of a renewal of large-scale military operations from the side of the Russian-terrorist groups," Poroshenko said his annual address to parliament.

"The military must be ready as much for a renewal of an offensive by the enemy in the Donbass as they are for a full-scale invasion along the whole length of the border with Russia. We must be truly ready for this," he said.

According to the BBC: "Russian Foreign Minister Sergei Lavrov, however, accused the authorities in Kiev of [jeopardizing] the Minsk agreement, by placing it 'under the constant threat of disruption' and by refusing to engage in direct dialogue with separatist leaders."

Reuters has a bit of background:

"A ceasefire has mostly held for the past four months, after the separatists spurned an earlier truce to launch an advance and seize more territory for their self-proclaimed state in what Russian President Vladimir Putin calls 'New Russia.'"The joint border stretches for more than 1,375 miles, most of it far from the area where there has been fighting."Copyright 2016 NPR. To see more, visit