Zelenskiy says Ukrainian drones have effectively closed Russian airspace

"Today, we want to warn every airline that uses Russian airspace, every insurer, everyone who still uses key Russian airports: the Russian sky is becoming completely dangerous," Zelenskiy said in his nightly video address.Ukraine poses no threat to civil aviation, he said, "but there will be drones in Russia's skies and due notice must be taken"."Although Russian authorities are not properly announcing it, Russian airspace will effectively be closing. The war started by Russia is closing its own skies," Zelenskiy added.Russia has stepped up its air attacks on Kyiv and other cities in recent weeks, with Moscow's latest strike killing 12 people and injuring many more, the sixth straight day of intense assaults on the Ukrainian capital.Ukraine has responded with frequent drone strikes on Russian targets, many associated with the country's oil industry as well as retail sites.(Reporting by Ron Popeski and Oleksandr Kozhukhar; Editing by Bill Berkrot)