An order to transform Russia's army into the second largest in the world is needed to address growing threats on the nation's western borders and instability to the east, the Kremlin says.
President Vladimir Putin has ordered the regular size of the Russian army to be increased by 180,000 troops to 1.5 million active servicemen in a move that would make it the second largest in the world after China's.
"This is due to the number of threats that exist to our country along the perimeter of our borders," Kremlin spokesman Dmitry Peskov told reporters on a conference call.
"It is caused by the extremely hostile environment on our western borders and instability on our eastern borders. This demands appropriate measures to be taken."
According to data from the International Institute for Strategic Studies, a leading military think tank, such an increase would result in Russia leapfrogging the US and India in terms of the number of active combat soldiers it has at its disposal.
The move, the third time Putin has expanded the army's ranks since sending his military into Ukraine in February 2022, comes as Russian forces push forward in eastern Ukraine on parts of a vast 1000km frontline and try to eject Ukrainian forces from Russia's Kursk region.
Andrei Kartapolov, chairman of Russia's lower house of parliament's defence committee, said on Monday that part of the rationale for the expansion was to set up new structures and military units to improve security in the northwest of Russia after neighbouring Finland joined the NATO alliance.
Russia has also expressed concerns about what it describes as the growing US-backed militarisation of Japan and potential plans to deploy US missiles there.
Meanwhile Russian forces launched missiles at energy infrastructure in Ukraine's northeast Sumy region on Tuesday, after carrying out a drone strike overnight.
The attack cut power in some districts and forced authorities to resort to back-up power systems.
According to preliminary estimates, Russian forces used at least four missiles in the latest attack.
The Ukrainian air force said Russia launched 51 drones to attack the country on Tuesday and its air defences had shot down 34 of them in five regions.
The overnight attack did damage in the Konotop, Okhtyrka and Sumy districts and the critical infrastructure facilities were using back-up power systems, regional officials said via the Telegram messaging app.
Sumy's acting mayor Artem Kobzar said there were no casualties in the city.
Ukraine's energy ministry said the attack caused a fire at a power substation and cut power to more than 281,000 consumers. The power had since been partially restored, it said.