Azerbaijan Defense Ministry said on Saturday that Armenian army tried to raid Azerbaijan’s military positions.
Azerbaijan positions came under fire from 82-millimetre mortars, according to the statement of the ministry.
One soldier, Elsen Memmedow was pronounced dead after the attack.
3 other soldiers were wounded as a result of gunfire.
The injured were taken to a hospital and are said to be in good condition.
Four Armenian servicemen were killed and 16 were injured, 10 of the injured are in critical condition.
The conflict between the two countries started with Armenia's territorial claims against Azerbaijan in 1988. War quickly broke out and Armenian armed forces occupied 20 percent of Azerbaijan, including the Nagorno-Karabakh region and seven surrounding districts.
The two countries signed a ceasefire agreement in 1994.
Armenia has not yet applied the UN Security Council's four resolutions on the liberation of the Nagorno-Karabakh and the surrounding regions.