Three days after moving to annex four regions of Ukraine, the Kremlin said Monday it would need to carry out consultations on defining the borders of two of the territories.

"We will continue to consult with people who live in these areas," Kremlin spokesman Dmitry Peskov told reporters, referring to the southern Kherson and Zaporizhzhia regions.

He said he could not specify what format the consultation would take.

Russia's inability to say whether it is claiming all of the occupied regions or only those portions controlled by its forces has highlighted the rushed and confused nature of the annexations, which Ukraine and the West have denounced as an illegal land grab.

Ukraine has made significant gains even since Friday's Kremlin annexation ceremony – including, on Monday, in Kherson region, where a Russian-installed official said Ukrainian forces had made breakthroughs and the situation was tense.