Russia said on Wednesday it had seen a significant jump in the number of men signing contracts to join the military since last month's deadly attack on a concert hall near Moscow where a gunman killed at least 144 people.

Russia has repeatedly sought to blame the attack on Ukraine, its opponent in a war now well into its third year, despite denials from Kyiv and a claim of responsibility by Islamic State militants for the massacre at the Crocus City Hall.

In a statement, the Russian defence ministry said more than 100,000 people have signed contracts with the armed forces since the start of the year, including about 16,000 in the past 10 days alone.