Russia pounded a town in Ukraine’s northeast with artillery, rockets and guided aerial bombs Friday before attempting an infantry breach of local defences, authorities said, in a tactical switch that Kyiv officials have been expecting for weeks as the war stretches into its third year. Intense nighttime shelling targeted Vovchansk, in the Kharkiv region and less than 5 kilometres (3 miles) from the Russian border, regional Gov. Oleh Syniehubov said. The barrage prompted authorities to begin the evacuation of around 3,000 people.

Around dawn, Russian forces tried to pierce the Ukrainian defences near Vovchansk, Ukraine’s Defence Ministry said, adding that it had deployed reserve units to fend off the attack.

Analysts said the assault could mark the start of a Russian attempt to carve out a “buffer zone” that President Vladimir Putin vowed to create earlier this year to halt frequent Ukrainian attacks on Belgorod and other Russian border regions.

Ukraine had previously said it was aware that Russia was assembling thousands of troops along the northeastern border, close to the Kharkiv and Sumy regions. While the Kremlin’s forces have made their most recent ground thrust in eastern Ukraine, Ukrainian intelligence officials said they expected the Kremlin’s forces to attack in the northeast, too.

Though Russia likely can’t capture Kharkiv, Ukraine’s second-largest city, it could compel Ukraine to send more troops to the region, leaving other areas more vulnerable to attack. Also, forcing Ukrainian authorities to evacuate civilians is likely to create disruption and divert resources.

“The entire town is under massive shelling now, it is not safe to stay here,” Vovchansk administration head Tamaz Hambarishvili told Ukraine’s Hromadske Radio. The Ukrainian Defence Ministry said fighting against Russian sabotage and reconnaissance groups continued into the afternoon.