Ukraine's parliament tentatively backed a bill on Wednesday aimed at drafting more soldiers into the army, a deeply divisive proposal in a nation exhausted by fighting.

Kyiv's military had for months been asking the government to draft more soldiers, to boost its dwindling ranks and reprieve its fatigued frontline troops.

After refusing outright to debate the bill last month, 243 lawmakers approved the measure in its first reading on Wednesday. The process of making it law could take weeks.

"This is not a final decision. There will be a second reading, amendments will be made to it," opposition lawmaker Oleksiy Goncharenko said on Telegram.

The original version of the bill, introduced by the government in December, would make it harder to avoid the draft and lower the age of military service from 27 to 25.

While it would also cut compulsory wartime service from an unlimited period to 36 months, the proposed changes sparked panic among those not yet called up.

After a year of grinding warfare that has failed to yield major territorial gains for either Russia or Ukraine, Moscow is throwing more manpower into the conflict.

President Volodymyr Zelensky said in December the military wanted to mobilize up to half a million people to battle the 600,000 or so Russians deployed in Ukraine. (AFP)