At least 49 Armenian troops have been killed in Azerbaijan border clashes and the death toll is likely to rise further, Armenian Prime Minister Nikol Pashinyan said on Tuesday.

Armenian defense ministry said on Tuesday that deadly clashes along its border with Azerbaijan had subsided but that the situation was still "tense" following the worst fighting since the arch-foes' war two years ago.

"The situation at several sections of the Armenian-Azerbaijani border remains extremely tense," the defense ministry said. "The enemy is continuing to attempt to advance its positions, despite a significant decrease in the intensity of fire."

Both Armenia and Azerbaijan have blamed each other for the escalation in hostilities.

Azerbaijan and Armenia agreed to a ceasefire early on Monday to halt a flare-up in hostilities over the Nagorno-Karabakh region, but it fell apart minutes later, Azerbaijani media said.

(With input from agencies)