Russia has not announced another mobilisation, seen as an unpopular measure, but has led an active campaign to attract more men into the military as its Ukraine offensive drags into a 19th month.

"According to data from the ministry of defence, 280,000 people have joined the Russian army on contracts from January 1," Medvedev said, according to the TASS news agency.

"Part of them were in the reserves, part of them volunteers and other categories," he added, during a visit to the Far Eastern Russian island of Sakhalin.

In early August, Medvedev said the army had recruited around 230,000 people since the start of the year.

AFP is not able to independently verify these numbers.

Since the spring, the Russian army has led a huge publicity campaign to recruit volunteers, with mass advertisements online and in Russian streets.

It has also sought to attract future soldiers by promising higher salaries.

In September last year, the Kremlin made a U-turn on promises not to announce a military draft, announcing a partial call-up to make up for losses on the Ukrainian front that led to the recruitment of 300,000 men.

But the announcement also triggered another wave of emigration from Russia, with hundreds of thousands believed to have fled abroad.

Medvedev, who led Russia from 2008 to 2012, has become one of Moscow's most hawkish voices in support of Putin's Ukraine offensive.