Russia says its have destroyed a large depot containing US and European weapons in western Ukraine's Ternopil region with Kalibr cruise missiles.
The announcement by Russia's defense ministry came as street fighting raged in the eastern city of Sievierodonetsk on Sunday.
Moscow has repeatedly hit out at the US and Europeans for supplying Ukraine with weapons. Earlier this month, President Vladimir Putin said Russia would strike new targets if the West supplied longer-range missiles to Ukraine.
In recent days, Ukrainian leaders have pleaded with Western countries to speed up deliveries of heavy weapons as Russian forces advance in the east.
The Interfax news agency said Sunday Russian forces had used Kalibr cruise missiles to attack the large depot. Russian forces also shot down three Ukrainian SU-25 fighter jets near Donetsk and Kharkiv in eastern Ukraine, it said.
Ukrainian sources reported smoke rising from the targeted depot, confirming explosions there.
"Residents of the Ternopil region, stay in shelters. Do not film, photograph or comment on social networks the consequences of the explosions," a local official wrote on social media to the residents.
Meanwhile, at least 22 people were wounded on Saturday when Russia struck the western town of Chortkiv, the regional governor said, all of them had been hospitalized.
According to the government, a military installation was partially destroyed in the attack and residential buildings were damaged.
Chortkiv, home to nearly 30,000 people before the Russians launched their operation, is located 140 kilometers north of the border with Romania and 200 kilometers southeast of Lviv, the largest city in western Ukraine.
In Severodonetsk, which has been the scene of fierce battles in recent weeks, fighting raged on.
Severodonetsk has been the epicenter of the battles in eastern Ukraine for control over the industrialized Donbas region, made up of the Luhansk and Donetsk provinces.
It is one of the last remaining parts still under Ukrainian control.
Pro-Russia forces said 300 to 400 Ukrainian forces were trapped with hundreds of civilians at the Azot chemical plant in an industrial area in the region.
In neighboring Donetsk province to the west, a huge cloud of smoke could be seen after an explosion in the city of Avdiivka, which houses another chemical plant.
Unlike eastern and southern Ukraine, which have borne the brunt of Russian firepower since Moscow began its operation on February 24, the west of the country has only seen sporadic attacks.
Russia strikes the west to target military installations housing weapons and military equipment supplied by Western countries.