An airfield in the Russian city of Kursk was targeted by a drone strike on Tuesday, a day after two air bases deep inside Russian territory were hit by Ukrainian drones.

Tuesday’s attack targeted an airfield that is about 80 miles from the Ukrainian border, causing a nearby oil tank to catch fire. The region’s governor said there were no casualties in the incident.

The attacks on Monday hit targets hundreds of miles inside Russia, the deepest Ukrainian drone strikes in Russian territory since the February 24 invasion. Later on Monday, Russia launched another massive missile barrage across Ukraine, targeting energy infrastructure.

The Kremlin said Tuesday that it’s taking necessary measures to counter the attacks. “Certainly, the push for such terror attacks to continue being openly announced by the Kiev regime is a risk. Of course, it is being taken into account, with all necessary measures being taken,” Kremlin spokesman Dmitry Peskov said, according to the Russian news agency TASS.

Kiev hasn’t officially taken credit for Monday’s attacks, but a senior Ukrainian official speaking on the condition of anonymity to The New York Times said Ukraine’s forces were responsible. The official said the drones were launched from Ukraine and claimed Ukrainian special forces inside Russia helped hit one of the targets. Mykhailo Podolyak, an advisor to President Volodymyr Zelensky, also hinted at Ukraine’s involvement.

Russia has demonstrated that it will significantly escalate its war in Ukraine in response to attacks on its territory. Moscow didn’t start launching large-scale missile strikes on Ukrainian energy infrastructure until after the truck bombing of the Crimean bridge in October.

The US has sought assurances from Ukraine that it won’t use US-provided arms to target Russian territory, with an exception for Crimea, which Russia has controlled since 2014. Russia said that the drones used in the Monday attacks were “Soviet-made.”

State Department spokesman Ned Price said Tuesday that the US was not helping Ukraine strike inside Russia. “We are not enabling Ukraine to strike beyond its borders. We are not encouraging Ukraine to strike beyond its borders,” he said.

This article was originally featured at Antiwar.com and is republished with permission.