Armenia's Prime Minister Nikol Pashinyan said 49 Armenian service personnel died during overnight clashes with Azerbaijan, the Interfax news agency reported.
In a speech to Armenia's parliament, Pashinyan said Baku had attacked Armenia's positions overnight and that fighting was ongoing.
Both Armenia and Azerbaijan have blamed each other for the escalation in hostilities, the latest dispute in decades-old tensions between the countries over the disputed Nagorno-Karabakh region.
(Reporting by Reuters; Editing by Alison Williams)