Russia's parliament on Wednesday passed a law scrapping an upper age limit for people signing up to join the army, in a sign Moscow may be looking to recruit more troops for its military campaign in Ukraine.

Under current legislation, only Russians aged 18 to 40 and foreign nationals aged 18 to 30 have the right to sign their first military service contract.

The lower and upper houses of parliament backed the bill in all the necessary readings, after which Russian President Vladimir Putin must sign it into law.

This comes as Russia has announced over 1000 troop deaths in its military operation in Ukraine, launched February 24, and has vowed to continue fighting for as long as it takes.

The UK Ministry of Defence says the real number of Russian losses is approximately 15,000.

"We need to strengthen our armed forces, to help the defence ministry. Our supreme commander-in-chief (Putin) is doing everything to make the army win and increase its effectiveness," speaker Vyacheslav Volodin said, as quoted on the State Duma lower house website.

The law refers to people voluntarily joining the armed forces, not young men doing compulsory national service.

"Highly professional specialists are needed to use high-precision weapons and operate weapons and military equipment" and such specialists may be aged 40 to 45, said a note accompanying the draft bill.

The note said the amendment would also help attract those in civilian professions to join the army, including medics, engineers and communications experts.

Russian Defence Minister Sergei Shoigu said Tuesday that Moscow "will continue the special military operation until all the objectives have been achieved," referring to military action in Ukraine.