Azerbaijan is carrying out major military exercises close to the disputed Nagorny Karabakh frontline with Armenia, the country's defence ministry said Tuesday. "The armed forces of Azerbaijan have started the next stage of large-scale military exercises in the frontline zone," the defence ministry said in a brief statement. The exercises -- which include both land and air forces -- will last until the end of the week, the statement said. Armenia-backed separatists seized Nagorny Karabakh from Azerbaijan in a war in the 1990s that left some 30,000 dead, and no final peace deal has been signed since a 1994 ceasefire. Frequent clashes between Armenian and Azerbaijani troops along their border and in the disputed region of Nagorny Karabakh -- with 15 people reportedly killed last year from both sides -- highlight the risk of a fresh conflict between the arch-foes. Flush with petrodollars, oil-rich Azerbaijan has threatened to take back the disputed region by force if negotiations do not yield results, while Armenia has vowed massive retaliation against any military action. Azerbaijan held similar exercises close to the frontline to test new weaponry in February, according to an earlier statement from the defence ministry. Last month forces belonging to the region's Armenian-backed administration staged their own military exercises, local media reported.