In an update, the governor of Lviv Maksym Kozytskyy said the death toll had risen from nine to 35, and that 134 were injured in a Russian air strike on a large Ukrainian military base near the Polish border on Sunday, local Ukrainian authorities said, in what appeared to be the westernmost attack of the war.

Foreign military instructors have worked in the past at the Yavoriv International Center for Peacekeeping and Security. It was not clear if any were present at the time.

A Ukrainian Defence Ministry representative told Reuters the ministry was still trying to establish if any of the foreign instructors were at the facility at the time of the attack.

The military training facility, the biggest in the western part of the country and traditionally the site of joint drills with NATO, is located less than 25 km (15 miles) from the Polish border.

The Kremlin did not immediately reply to a request for comment on the missile strike so close to the border with NATO.

Regional governor Maksym Kozytskyy said Russian planes fired around 30 rockets at the facility, adding that some were intercepted before they hit.

A Reuters witness saw 19 ambulances with sirens on driving from the direction of the base following the strike and black smoke rising from the area.

"Poland condemns any element of aggression against Ukraine, including shelling of the Yavoriv base," Polish foreign ministry spokesman said in a message sent to Reuters.

The mayor of another city in western Ukraine, Ivano-Frankivsk, said that Russian troops also continued to hit its airport on Sunday. According to preliminary reports, there were no casualties.