Russia will begin a partial mobilization, President Vladimir Putin announced Wednesday morning, with reservists to be called in for army service.

"I consider it necessary to support the proposal of the Ministry of Defense and the General Staff to conduct partial mobilization in the Russian Federation," Putin said, adding that the mobilization begins Wednesday.

"I shall stress that Russian citizens called up as part of mobilization will be given all the benefits of those serving under contract.”

The Russian president vowed to “liberate” the Donbas province of eastern Ukraine, and laid out plans for the formal annexation of areas captured from Ukraine since Russia’s invasion began in February.

"Our aim is to liberate Donbas," Putin said Wednesday.

On Tuesday, the Russian-backed leaders of four Ukrainian provinces occupied by Russia announced that they will conduct referendums on possible annexation by Russia. The referendums are slated to be held later this week.

The four provinces make up some 15% of Ukraine’s territory.

The Kremlin announced that if the referendums back annexation, Russia will use “all means” to maintain control over its new territories.