Fierce fighting raged for a second day following a flare-up of a decades-old conflict in the Caucasus region of south-eastern Europe.
Dozens of deaths were reported in battles between forces fighting for Armenia and Azerbaijan on Monday.
At the heart of the conflict is a dispute over control of the mountainous region of Nagorno-Karabakh.
It is recognised as part of Azerbaijan, but has been controlled by ethnic Armenians since a war ended in 1994.
Tens of thousands of people died during that war and a million others were forced to leave their homes.
They are also keen to maintain stability because major gas and oil pipelines run through the area.
The latest intense fighting began on Sunday, with both Armenia and Azerbaijan blaming each other for the escalation.
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Both parties said they had mobilised more soldiers and declared martial law in some areas.
The fighting is the heaviest seen in the conflict since 2016, when at least 200 people were killed in clashes.
Where do other countries stand?
Turkey has declared its support for Azerbaijan, while Russia - which has military bases in Armenia but is also friendly with Azerbaijan - called for an immediate ceasefire.
Armenia has accused Turkey of providing direct military support to help Azerbaijan gain control of territory - a claim denied by Azerbaijan.
On Monday, Turkish President Recep Tayyip Erdogan called on Armenia to immediately end its occupation of the region and withdraw, saying this was the only course of action that would secure peace.
Mr Erdogans chief adviser, Ilnur Cevik, also said Turkey had told its Azeri allies to go as far as they wanted.