By Yuras Karmanau
Associated Press

LVIV, Ukraine — After days of regrouping and reinforcing, the Russian military began a new and potentially climactic phase of the war in Ukraine by launching its long-feared, full-scale ground offensive to take control of the country’s industrial heartland, the Donbas, Ukrainian officials said.

The stepped-up assaults began Monday along a broad front of over 300 miles, Ukrainian officials said.

“The Russian troops have begun the battle for the Donbas,” Ukrainian President Volodymyr Zelenskyy announced in a video address. He said a “significant part of the entire Russian army is now concentrated on this offensive.”

Moscow-backed separatists have been fighting Ukrainian forces for eight years in the mostly Russian-speaking Donbas and have declared two independent republics that have been recognized by Russia. Russia has declared the capture of the Donbas to be its main goal in the war since its attempt to seize the capital, Kyiv, failed.

“No matter how many Russian troops are driven there, we will fight,” Zelenskyy vowed. “We will defend ourselves.”

Before the offensive got underway, Russia bombarded the western city of Lviv and other targets in what appeared to be an intensified bid to grind down the country’s defenses.

The Ukraine military’s general staff said Russian President Vladimir Putin’s forces had intensified assaults in the Luhansk and Donetsk regions — both part of the Donbas — and in the area of Zaporizhzhia.

On Monday morning, “almost along the whole front line of the Donetsk, Luhansk and Kharkiv regions, the occupiers attempted to break through our defenses,” Oleksiy Danilov, secretary of Ukraine’s national security council, told Ukrainian media. “Fortunately, our military is holding out. They passed through only two cities. This is Kreminna and another small town.”

There were street battles in Kreminna, and Russian forces took control of the city, according to Luhansk regional military administrator Serhiy Haidai. He told Ukrainian TV that heavy artillery fire set seven residential buildings on fire and targeted a sports complex where the nation’s Olympic team trains.

Haidai said that before advancing, Russian forces “just started leveling everything to the ground.” He said his forces retreated to regroup and keep fighting.

Meanwhile, in the besieged southern port city of Mariupol, Denys Prokopenko, commander of the Azov Regiment of the Ukrainian National Guard that was holding out against Russian forces, said in a video message that Russia had begun dropping bunker-buster bombs on the Azovstal steel plant where the regiment was holed up.

The sprawling plant contains a warren of tunnels where both fighters and civilians are sheltering. It is believed to be the last major pocket of resistance in the shattered city.

In Lviv, a city close to the Polish border that has seen only sporadic attacks during almost two months of war, at least seven people were reported killed in missile strikes. Lviv has been a haven for civilians fleeing the fighting elsewhere. And to the Kremlin’s increasing anger, it has also become a major gateway for NATO-supplied weapons.

The attack on Lviv hit three military infrastructure facilities and an auto shop, according to the region’s governor, Maksym Kozytskyy. He said the wounded included a child.

A hotel sheltering Ukrainians who had fled the fighting in other parts of the country was also badly damaged, Lviv Mayor Andriy Sadovyi said.

“The nightmare of war has caught up with us even in Lviv,” said Lyudmila Turchak, who fled with two children from the eastern city of Kharkiv.

The biggest city in western Ukraine and a major transportation hub, Lviv is about 50 miles from Poland, a NATO member.

Russia has complained about the increasing flow of Western weapons to Ukraine and warned that such aid could have consequences. On Russian state media, some anchors have charged that the supplies amount to direct Western engagement in the fight against Russia.

Kharkiv, Ukraine’s second-largest city, was hit by shelling that killed at least three people, according to Associated Press journalists on the scene. One of the dead was a woman who appeared to be going out to collect water in the rain. She was found with a water canister and an umbrella by her side.

Moscow said its missiles struck military targets in eastern and central Ukraine including ammunition depots, command headquarters, and groups of troops and vehicles. It reported that its artillery hit hundreds of Ukrainian targets, and that warplanes conducted 108 strikes on troops and military equipment. The claims could not be independently verified.

Gen. Richard Dannatt, a former head of the British Army, told Sky News that Russia was waging a “softening-up” campaign ahead of the Donbas offensive.

A senior U.S. defense official, speaking on condition of anonymity to discuss the Pentagon’s assessments of the war, said there are now 76 Russian combat units, known as battalion tactical groups, in eastern and southern Ukraine, up from 65 last week. That could translate to around 50,000 to 60,000 troops, based on what the Pentagon said at the start of the war was the typical unit strength of 700 to 800 soldiers.

The capture of Mariupol is seen as key. If Russian forces succeed in taking full control of the city, that could free up nearly a dozen battalion tactical groups for use elsewhere in the Donbas, the U.S. defense official said.

It also would deprive Ukraine of a vital port, and complete a land bridge between Russia and the Crimean Peninsula, seized from Ukraine from 2014.