KYIV, UKRAINE -- Russian forces began a renewed ground assault in Ukraine's northeast, killing and injuring several people and forcing more than 1,700 civilians to evacuate from the Kharkiv region, officials said Saturday.

Artillery, mortar, and aerial bombardments hit more than 30 different towns and villages, leaving at least three people dead and five others injured, said Kharkiv Gov. Oleh Syniehubov.

Ukraine rushed reinforcements to the Kharkiv region on Friday to hold off a Russian attempt to breach local defenses, authorities said.

Ukrainian forces also launched a barrage of drones and missiles on Saturday night, Russia鈥檚 Ministry of Defense said, with air defense systems downing 21 rockets and 16 drones over Russia鈥檚 Belgorod, Kursk and Volgograd regions. One person died in a drone strike in the Belgorod region, and another in the Kursk region, local officials said.

Another strike set ablaze an oil depot in Ukraine鈥檚 Russian-occupied Luhansk region, killing three people and injuring eight more, Leonid Pasechnik, the region鈥檚 Moscow-installed leader said on the messaging app Telegram on Saturday.

Russian forces stepped up their bombardment of Kharkiv, Ukraine鈥檚 second-largest city, in late March. Friday鈥檚 attack signaled a tactical switch in the war by Moscow that Ukrainian officials had been expecting for weeks.

Russian military bloggers said the assault could mark the start of a Russian attempt to carve out a 鈥渂uffer zone鈥 that President Vladimir Putin vowed to create earlier this year to halt frequent Ukrainian attacks on Belgorod and other Russian border regions.

Ukrainian President Volodymyr Zelenskyy confirmed Friday evening that Russian forces were expanding their operations. He also called on the country鈥檚 Western allies to ensure that promised deliveries of military aid would swiftly reach the front lines.

鈥淚t is critical that partners support our warriors and Ukrainian resilience with timely deliveries. Truly timely ones,鈥 he said in a video statement on X. 鈥淎 package that truly helps is the actual delivery of weapons to Ukraine, rather than just the announcement of a package.鈥

The Kremlin鈥檚 forces have repeatedly sought to exploit Ukraine鈥檚 shortages of ammunition and personnel as the flow of Western military aid to Kyiv has tapered off in recent months, with promised new support still yet to arrive.

Ukraine previously said it was aware that Russia was assembling thousands of troops along the northeastern border, close to the Kharkiv and Sumy regions. Intelligence officials also said they had expected an attack there though Russia鈥檚 most recent ground offensive had been focused on parts of eastern Ukraine farther south.

While Russia鈥檚 gains in the region have so far been limited, analysts at the U.S. think tank Institute of the Study of War described them Friday as 鈥渢actically significant.鈥

They said Russia had only 鈥渃ommitted relatively limited manpower to their initial assaults鈥 but that the offensive in Kharkiv 鈥渋s meant to ... (draw) Ukrainian manpower and materiel from other critical sectors of the front in eastern Ukraine.鈥

The Russian military could also try to cut key supply routes and try to blockade Kharkiv, home to roughly 1.1 million people and only about 30 kilometres (about 20 miles) south of the border.

In the war's early days, Russia made a botched attempt to quickly storm Kharkiv but retreated from its outskirts after about a month. In the fall of 2022, seven months later, Ukraine鈥檚 army pushed them out of Kharkiv. The bold counterattack helped persuade Western countries that Ukraine could defeat Russia on the battlefield and merited military support.