Russia had been planning Monday's missile strikes on Ukrainian cities since the start of October, Ukrainian military intelligence said.

"According to the military intelligence of Ukraine, the Russian occupying forces received instructions from the Kremlin to prepare massive missile strikes on the civilian infrastructure of Ukraine on October 2 and 3," the intelligence arm of the Ukrainian defence ministry said in a statement.

"The military units of the strategic and long-range aviation received orders to prepare for the task of massive missile attacks. The objects of critical civil infrastructure and the central areas of densely populated Ukrainian cities were identified as targets." (Reporting by Max Hunder, Editing by Timothy Heritage)