NATO Secretary General Jens Stoltenberg on Friday denounced Russia's "illegal" annexation of four regions of Ukraine, stressing that allies would never recognize these territories as part of Russia.

"Ukraine has the right to recover these lands that were occupied by force, and we will support it to continue liberating these lands," Stoltenberg said at a press conference after President Vladimir Putin officially signed the annexation of Donetsk, Lugansk (east), Zaporizhia and Kherson (south).