Russia pulled some troops out of southern Ukraine and back into its own territory to try to fend off an escalating incursion by Kyiv’s forces, a Ukrainian official said on Tuesday.

Ukraine’s ongoing surprise attack has triggered scrambling in Moscow where President Vladimir Putin has expressed anger after Kyiv snatched dozens of settlements and huge areas of territory in the Kursk and Belgorod regions of southern Russia.

“Russia has relocated some of its units from both Zaporizhzhia and Kherson regions of Ukraine’s south,” Dmytro Lykhoviy, a Ukrainian army spokesman, told POLITICO.