Foreign military instructors work at the military base in eastern Ukraine that has been attacked by Russia, Ukraine's Defence Minister Oleksii Reznikov says.
Local officials say eight missiles struck the International Centre for Peacekeeping and Security, 10km (6 miles) from the Polish border.
"Information about the victims is being clarified," Reznikov says.
A witness told Reuters news agency they saw 19 ambulances with their sirens on driving from the direction of the military base.
"This is new terrorist attack on peace and security near the EU-Nato border," Reznikov wrote on Twitter.
Russian forces launched a missile attack on a large Ukrainian military facility near the Polish border on Sunday, Ukrainian officials said, in what appeared to be the westernmost attack of the war.
"The occupiers launched an air strike on the International Center for Peacekeeping and Security" in Yavoriv, the Lviv regional military administration said in a statement. "According to preliminary data, they fired eight missiles."
The 360 square-km (140 square-mile) facility less than 25 km (15 miles) from the Polish border, is one Ukraine's biggest and the largest in the western part of the country.
The United States and NATO have regularly sent instructors to the range, also known as the International Peacekeeping and Security Center, to train Ukrainian military personnel. The facility has also hosted international NATO drills.
Ukraine held most of its drills with NATO countries there before the invasion. The last major exercises were in September.
The Russian invaders appear to have struggled far more than expected against determined Ukrainian fighters. Still, Russia’s stronger military threatens to grind down Ukrainian forces.
Thousands of soldiers on both sides are believed to have been killed along with many civilians, including at least 79 Ukrainian children, its government says. At least 2.5 million people have fled the country, according to the United Nations refugee agency.
