Nearly 100 people, including civilians, died as battles raged between Armenian and Azerbaijani forces in the disputed Nagorno-Karabakh region.
The mountainous enclave is recognized as part of Azerbaijan, but has been run by Armenians since a war ended in 1994.
The self-proclaimed republic has reported 84 military deaths since Sunday, as well as civilian casualties.
Azerbaijan did not disclose its military casualties, but confirmed seven civilian deaths.
The fighting that began three days ago now appears to extend from Nagorno-Karabakh.
On Tuesday, the Armenian Defense Ministry said a passenger bus was hit by an Azerbaijani drone in the eastern Armenian city of Vardenis. There have been no reports of casualties.
Azerbaijan had previously said that two Azerbaijani civilians were killed in the Armenian bombing raids in Azerbaijan on Monday, following the deaths of five members of the same family the day before.
What’s behind the conflict?
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The fighting is the heaviest seen in the conflict since 2016, and the United Nations Security Council will hold emergency talks on the matter later on Tuesday.
Both Armenia and Azerbaijan – which have already mobilized more soldiers and declared martial law in some areas – blame each other for starting the fighting.
There are growing concerns that other countries may be directly involved in the conflict in the strategic Caucasus region.
Turkey has already openly supported Azerbaijan, while Russia – which has a military base in Armenia – has called for an immediate ceasefire.
Nagorno-Karabakh: key facts
- A mountainous region of approximately 4,400 sq km (1,700 sq miles)
- Traditionally inhabited by Christian Armenians and Muslim Turks
- In Soviet times, it became an autonomous region within the republic of Azerbaijan
- Internationally recognized as part of Azerbaijan, but the majority of the population is ethnic Armenian
- It is estimated that one million people were displaced by the war in 1988-1994 and around 30,000 killed
- Separatist forces have captured some extra territories around the enclave in Azerbaijan
- The stalemate has largely prevailed since the 1994 ceasefire
- Turkey openly supports Azerbaijan
- Russia has a military base in Armenia