Ukrainian former tennis player Sergiy Stakhovsky enlisted in his country's reserve army last week prior to Russia's invasion, he said, despite a lack of military experience, although he can handle a gun.
Russia's invasion by land, air and sea on Thursday followed a declaration of war by President Vladimir Putin.
The 36-year-old Stakhovsky, who won four ATP titles and had a shock win over Roger Federer in the second round of Wimbledon in 2013, said on Saturday he was willing to take up arms in Ukraine's defence.
