Ukraine is using Western-supplied long-range weapons and 155mm “smart” shells to hit Russian ammo dumps and supply lines, forcing Moscow to rethink how it supplies fuel and ammunition to the front line, a Ukrainian general said on Thursday.

Ukraine said earlier on Thursday its forces had struck two military checkpoints and a landing point in a town in Russian-occupied territory in southern Ukraine, the latest attack Kyiv says its forces have carried out deep in areas held by Russia in the last two weeks.

General Oleksiy Gromov told a news conference that Western-supplies of weapons were critical to Ukrainian strikes and singled out U.S.-made High Mobility Artillery Rocket Systems (HIMARS) that Kyiv began receiving last month.

HIMARS have a longer range and are more precise than the Soviet-era artillery that Ukraine had in its arsenal.

“We are decreasing the enemy’s potential, hitting his logistics supply, hitting his ammunition… The enemy is being forced to change its system for supplying ammunition and fuel,” Gromov said.

“Right now the enemy is looking at placing brigade-level ammunition dumps no closer than 100 kilometres (62 miles) from the front line, and depots at corps-level at distances of over 150 km.”

The West has supplied Ukraine with longer-range heavy artillery and multiple launch rocket systems to help Kyiv hold out despite Russian artillery supremacy in terms of numbers and ammunition.

Russia’s foreign ministry on Thursday criticised the United States and Britain for helping train Ukraine‘s armed forces and accused Washington of providing Ukraine with instructors to help Kyiv’s forces use HIMARS.

Gromov’s assertions could not be independently verified by Reuters. But they suggest Western weapons are having a big impact on the battlefield and could indicate a subtle shift in the war’s dynamic after nearly five months.

“Apart from MLRS, we are actively using 155mm smart shells, with self-aiming elements, with the help of which almost 30 of the enemy’s armoured objects have already been hit,” Gromov said.

Russia, which invaded Ukraine on Feb. 24, has captured a chunk of territory in southern Ukraine and used its artillery supremacy in the east to make gradual territorial gains, eventually capturing Luhansk region.