MOSCOW (Reuters) - Armenia's defence ministry said on Tuesday that 12 of its soldiers had been captured by Azerbaijan, the Interfax news agency quoted it as saying.

       The Azeri foreign ministry said in a separate statement that it considers Armenia guilty of deliberate escalation of tensions at the two countries' border.

       Earlier on Tuesday, Armenia asked Russia to help defend its territorial sovereignty against Azerbaijan and said a heavy border clash between Azeri and Armenian forces was underway.

       (Reporting by Polina Devitt and Nailia Bagirova; Editing by Catherine Evans)