Ukraine’s Defense Minister said that Russian forces launched an attack on eastern Ukraine on Monday in an attempt to break through Ukrainian lines in the Donbass region.

“This morning, almost along the front line of the Donetsk, Luhansk and Kharkiv regions, the occupiers tried to break through our defenses,” Oleksiy Danilov said in televised statements.

“They started their attempt to start the active phase this morning,” he added.

The Pentagon did not contest the Ukrainian reports, Monday, but described the attacks as “shaping operations” in preparation for a larger attack in the future.

“We continue to consider that what we’re seeing is part of shaping operations and that the Russians continue to create the conditions for what they believe will be an eventual success on the ground,” Pentagon spokesman John Kirby told reporters.

We believe that the Russians are shaping and preparing the conditions for future offensive operations. We also see that there is active fighting going on in the Donbass – as it has in the past several weeks.”

Donbass, made up primarily of the Luhansk and Donetsk states along Ukraine’s eastern border with Russia, has been the site of intermittent fighting since Russia’s annexation of Crimea in 2014 and Moscow’s simultaneous support for Donbass separatist movements.

After Russian forces failed to seize Kyiv last month, the Kremlin announced it was refocusing its efforts on capturing Donbass, while continuing to bomb all of Ukraine.

Monday’s reports of fighting in the area come days after Russian forces were massed near the city of Izyum in Kharkiv province just outside Donbass.

The attack also comes just hours after a large-scale Russian bombing campaign targeting targets across Ukraine, including Far west to Lviv, Near the Polish border. The Russian authorities reported bombing military targets in Kharkiv, Zaporizhzhya, Dnipro and Mykolaiv, as well as in Donetsk in the heart of the Donbass.

Meanwhile, the Pentagon estimates that Russia has beefed up its forces in southern and eastern Ukraine, adding tens of thousands of troops to the region via at least a dozen new tactical groups.

Mariupol, a strategic port city in southern Donbass, continued to withstand the Russian onslaught, although its defenders dwindled. Ukrainian control of the city is the main obstacle to the entry of Russian forces in Crimea into the Donbass.

Experts predicted that any large-scale Russian attack on the Donbass would occur after the capture of Mariupol.

with wire