Zelensky warned Russian airspace, Mr. Putin called it a "declaration of war"

While Mr. Zelensky warned that Russian airspace could be "locked" because of Ukrainian drones, Mr. Putin said that this was a "declaration of war".

"We want to warn every airline using Russian airspace, every insurance company, every individual still using Russia's key airports that Russian skies are becoming extremely dangerous," Ukrainian President Volodymyr Zelensky said on the evening of September 1.

He said Ukraine does not threaten civil airlines, but "drones will appear in the Russian sky and relevant parties need to pay attention to this warning."

"Even though the Russian government did not make a specific announcement, Russian airspace will in fact be closed. Russia is closing its own skies with the war they started," President Zelensky added.

Russian President Vladimir Putin immediately responded, calling the statements from his Ukrainian counterpart "a declaration of war".

"They asked us to restart negotiations, but no one negotiates with the threats," he said.

In a subsequent press conference on the sidelines of the Shanghai Cooperation Organization conference in Kyrgyzstan, President Putin also commented on information that the Ukrainian military used British-made drones to attack targets on Russian territory.

When asked whether Russia would attack British military facilities if the British government continued to supply drones to Ukraine, Mr. Putin did not rule out this option, but told reporters that it was "a military secret."

Threats to increase pressure on each other in the air war between Russia and Ukraine could pose risks for airlines.

Aviation risk consulting firm Osprey Flight Solutions warns clients that while the majority of Ukraine's drone and missile strikes are likely to take place within 300 km of the border, daily attacks deep into Russia's interior, including near Moscow and St. Petersburg, will almost certainly continue throughout 2026.

"Ukraine's raids deep into Russia's interior may increase in the short term. In areas related to the Ukrainian war, the risk of miscalculation or shooting at the wrong target is very large," the company said.