By Pavel Polityuk and Sergiy Chalyi
KYIV/NOVOSOFIIVKA, Ukraine (Reuters) -A third Russian airfield was set ablaze on Tuesday by a drone strike, a day after Ukraine demonstrated an apparent new ability to penetrate hundreds of kilometres into Russian air space with attacks on two bases.
Officials in the Russian city of Kursk, around 90 km (60 miles) north of the Ukraine border, released pictures of black smoke above an airfield in Tuesday's early hours after the latest strike. The governor said an oil storage tank had gone up in flames, but there were no casualties.
On Monday, Russia said it had been hit hundreds of kilometres from Ukraine by what it said were Soviet-era drones - at Engels air base, home to Russia's strategic bomber fleet, and in Ryazan, a few hours' drive from Moscow.
Ukraine did not directly claim responsibility for the strikes, but nonetheless celebrated them.
In Washington, U.S. State Department spokesman Ned Price said on Tuesday, "We are not enabling Ukraine to strike beyond its borders. We are not encouraging Ukraine to strike beyond its borders."
He added that there was no confirmation the strikes were carried out by Ukraine.
Price said the United States has not provided Ukraine with weapons that are to be used within Russia.
"We have been very clear that these are defensive supplies," Price said.
'SMOKING'
Russia's defence ministry said three service members were killed in the attack at Ryazan. Although the attacks struck military targets, it characterised them as terrorism and said the aim was to disable its long-range aircraft.
The New York Times, citing a senior Ukrainian official, said the drones involved in Monday's attacks were launched from Ukrainian territory, and at least one of the strikes was carried out with the help of special forces close to the base.
Ukraine never publicly acknowledges responsibility for attacks inside Russia. Asked about the strikes, Defence Minister Oleskiy Reznikov repeated a longstanding joke blaming carelessness with cigarettes. "Very often Russians smoke in places where it's forbidden to smoke," he said.
Ukrainian presidential adviser Oleksiy Arestovych went further, noting that Engels is Russia's only base fully equipped for the fleet of huge bombers Moscow has used to attack Ukraine.
"They will try to disperse (strategic aircraft) to airfields, but all this complicates the operation against Ukraine. Yesterday, thanks to their 'unsuccessful smoking', we achieved a very big result," he said.
The damage to the warplanes also caused grumbling among Russian military bloggers, whose social media posts can provide a window into the mood in Russia on the course of the war, which began more than nine months ago with Russian forces invading Ukraine.
"And I, a naive civilian fool, thought that planes were kept under concrete shelters during war, no?" wrote Vladlen Tatarsky. "It turns out that small drones, the danger from which was so neglected, can attack strategic aircraft."
NEW BARRAGE
The huge Tupolev long-range bombers that Russia stations at Engels form a big part of its strategic nuclear arsenal, similar to the B-52s deployed by the United States during the Cold War. Russia has used them in its campaign since October to destroy Ukraine's energy grid with near weekly waves of missile strikes.
The Engels base, near the city of Saratov, is at least 600 km (372 miles) from the nearest Ukrainian territory.
Russia responded to Monday's attacks with what it called a "massive strike on Ukraine's military control system", though it did not identify any specific military targets for what Ukraine called Moscow's latest strikes on civilian infrastructure.
Moscow claims military justification for attacks on Ukraine's civil infrastructure. Kyiv says the strikes are intended to hurt civilians, a war crime.
Missiles across Ukraine destroyed homes and knocked out power, but the impact seemed less severe than barrages last month that pitched millions of Ukrainians into darkness and cold.
Meanwhile on the battlefields of eastern, northeastern and southern Ukraine, Russian forces kept up their shelling of towns and villages, the Ukrainian military said in its Tuesday evening report.
On Tuesday, Zelenskiy visited troops in the eastern Donbas region that has seen the war's heaviest fighting.
He praised soldiers in a selfie video filmed in front of a sign on the road outside Sloviansk, near the city of Bakhmut that Russian forces have been trying to encircle for weeks. He also presented medals and shook hands with troops in a hangar.
RESISTANCE
Also on Tuesday, the U.S. deputy secretary of state said Russia must remove all its troops from Ukraine.
Wendy Sherman, speaking at an event in Rome, said the United States had sufficient arms stockpiles to keep helping Ukraine, and that Western states backing Kyiv must "stay the course".
No political talks are under way to end the war. Moscow insists it will not negotiate unless Kyiv and the West accept its sovereignty over Ukrainian lands it claims, while Kyiv says Russia must leave all its territory.
Kremlin spokesman Dmitry Peskov said on Tuesday talks would only be possible when Russia achieves the goals of its "special military operation", which he did not define.