Both Armenia and Azerbaijan accused each other of shelling in breach of a Russian-brokered ceasefire.
As Armenia and Azerbaijan accused each other of violating a temporary ceasefire within minutes of it coming into force on Saturday, one expert says intervention from the United States and European nations is needed for a truce to hold.
To bolster the effectiveness of a ceasefire "more active entry and lobbying for stabilisation from the third co-chair of the Minsk Group - the United States," would be needed, Laurence Broers, Caucasus programme director at Conciliation Resources, told Euronews.
"We need a lot more action from European states to support humanitarian relief and a return to the negotiating table," he added.
Concerning outside players, Broers said, Russia "clearly doesn't have the leverage that it had four years ago" and that the entry of Turkey into the flare-up was a major new factor that would give Azerbaijan confidence to resist Russian brokerage "on terms that it doesn't particularly like".
Armenia and Azerbaijan blame each other for the latest flare-up in deadly violence, which has killed hundreds of people since it broke out on September 27.
The two countries agreed to a truce on Friday evening after 11-hour talks chaired by Russian Foreign Minister Sergei Lavrov in Moscow.
But in a statement released an hour after the truce started, the Azerbaijani Defence Ministry said that a number of populated areas were "under artillery fire by the Armenian armed forces". Azerbaijani authorities said on Sunday that nine civilians have been killed and over 30 wounded after Armenian forces fired missiles overnight on Ganja, Azerbaijan's second-largest city.
Armenia’s Defence Ministry denied any truce violations by the Armenian forces, accusing Azerbaijan of shelling the area near the town of Kapan in southeastern Armenia, killing one civilian. Azerbaijan’s Defence Ministry rejected the Armenian accusations as a "provocation".
The former Soviet states of Azerbaijan and Armenia fought a bloody war over the mountainous region of Nagorno-Karabakh in the early 1990s.
Thousands were killed on both sides. Hundreds of thousands of people were displaced.
The war ended with a truce in 1994, although there has been sporadic violence since.
To see the full interview with Broers take a look at the media player, above.