A Russian drone breached Nato airspace after flying into Poland before being shot down in Ukrainian territory, Ukraine's airforce have said.
The unmanned aircraft is said to have been circling the Ukrainian city of Yavoriv to assess the damage caused by a Russian strike on the Yavoriv military base near Lviv.
An attack over the weekend killed at least 35 people and injured at least 134, authorities said.
Yavoriv is located just 15 miles from the Polish border, but was targeted with more than 30 cruise missiles on Sunday.
A spokesperson for the Ukrainian forces said: "As we can see, the occupiers continue to carry out their provocative actions without hesitation, flying into the airspace of Nato member states."
According to The Times, Ukrainian military sources said they thought it was a Russian Forpost drone, which is not flown by any other country.
"There are no NATO personnel in Ukraine," a NATO official said, when asked if any NATO personnel were at the base.
Ukraine's government has pleaded with Nato to enforce a no-fly zone in their airspace, but Nato have so far declined over fears it would trigger a war against the Russian Federation.
Speaking on Thursday, Prime Minister Boris Johnson said bringing in the no-fly zone would cause direct conflict between Russia and Nato - something he was determined to avoid.
On Monday, health secretary Sajid Javid warned of a "severe response" if Russia encroached on Nato territory.
He said: "We've been very clear from the start, with our Nato allies, that if there is any kind of attack on Nato territory then it will be war with Nato and there will be a severe response.
Watch: Flashes from strikes on West Ukraine base seen from across Polish border
"Even if just a single toecap of a Russian soldier steps into Nato territory, then it will be war with Russia and Nato would respond.
"That hasn't changed throughout this conflict and there would be a significant response from Nato if there was any kind of attack from Russia.
"Our message has been very clear from the start. Any kind of attack, anything that touches Nato territory or impacts Nato in any significant way, then we would respond."