Moscow is declaring Ukraine's Donetsk, Luhansk, Kherson and Zaporizhzhia regions, largely or partly occupied by Russian or Russian-backed forces, to be part of Russia.
Asked by reporters if an attack by Ukraine on the territories Russia is claiming as its land would be considered an attack on Russia, Kremlin spokesman Dmitry Peskov said: "It would not be anything else.".
Russia is moving to annex the regions after holding what it called referendums in the occupied areas of Ukraine.
The exact details of Russia's annexation are unclear but it appears that Russia is laying claim to about 109,000 sq km (42,000 sq miles) of Ukrainian territory, or about 18%, in addition to Crimea, which Russia annexed in 2014.
Asked what would happen to the territory not under Russian control, Peskov said: "It is to be liberated.".
He said the whole of the Donetsk region would become part of Russia.
The conflict in eastern Ukraine began in 2014 after a pro-Russian president was toppled in Ukraine's Maidan Revolution and Russia annexed Crimea. »