Armenia and Azerbaijan on Wednesday accused each other of violating a truce, after the worst clashes since a 2020 war put in doubt a halting peace process between the arch foes.
Russia announced on Tuesday that it had negotiated a ceasefire following fighting that killed at least 100 Azerbaijani and Armenian troops.
But on Wednesday, Armenia's Defence Ministry said "the enemy re-launched its attack by using artillery, mortar, large-calibre firearms in the directions of Jermuk, Verin Shorzha" on the border.
"Despite a clear reaction from the international community over the situation, in fact Azerbaijan's military-political leadership continues its acts of aggression against the sovereign territory of Armenia, targeting both military and civilian infrastructure," Wednesday's statement said.
The Azerbaijani Defence Ministry said Armenian forces "violated the ceasefire... and shelled Azerbaijani positions near Kelbajar and Lachin with mortars and artillery."
Tuesday's escalation came as Yerevan's closest ally Moscow is distracted by its six-month-old war against Ukraine.
Russian President Vladimir Putin's spokesman, Dmitry Peskov, said that "Definitely, tensions persisted" on Wednesday on the Armenian-Azerbaijani border.
He said a delegation of the Collective Security Treaty Organisation (CSTO) — a Moscow-led grouping of ex-Soviet republics of Armenia, Belarus, Kazakhstan, Kyrgyzstan, Tajikistan, and Uzbekistan — was due to Yerevan later on Wednesday.
On Tuesday, Armenia's security council asked for military help from Moscow, which is obligated under the treaty to defend Armenia in the event of foreign invasion.
The Ukraine conflict changed the balance of force in the region as Russia — which deployed thousands of peacekeepers in the region afer the 2020 war — is increasingly isolated.
The European Union has since led the Armenia-Azerbaijan normalisation process, which involves peace talks, border delimitation and the reopening of transport links.
Analyst Gela Vasadze of the Georgian Strategic Analysis Centre said the latest escalation "has undone EU-led efforts to bring Baku and Yerevan closer to a peace deal."
"Brussels agreements are now practically nullified," he said, adding that the clashes "have further radicalised public opinion in both countries."
During EU-mediated talks in Brussels in May and April, Azerbaijan's Ilham Aliyev and Armenia's Nikol Pashinyan agreed to "advance discussions" on a future peace treaty.
In Yerevan, emotions ran high among relatives of wounded Armenian servicemen, as they gathered outside a military hospital on Tuesday night.
"We must fight for our lands, for our homeland and for our country. Victory will be ours, if not today, then tomorrow. We are unbreakable," one of the relatives, Sokrat Khachaturyan, 65, told AFP.
Economist Arman Mkhitaryan said that "a new war was to be expected of course, seeing the accumulation of the Azerbaijani (military at the border)."
"The capabilities and the potential of the current (Armenian) government are not enough to take on today's challenges."
On Tuesday, Armenia appealed to world leaders for help over the latest fighting.
The European Union, United States, France, Russia, Iran, and Turkey all expressed concern over the escalation and called for an end to fighting.
The Azerbaijan-Armenia conflict over Nagorno-Karabakh
The neighbours fought two wars — in the 1990s and in 2020 — over the disputed Nagorno-Karabakh region, Azerbaijan's Armenian-populated enclave.
The six weeks of fighting in autumn 2020 claimed the lives of more than 6,500 troops from both sides and ended with a Russian-brokered ceasefire.
Under the deal, Armenia ceded swathes of territory it had controlled for decades and Moscow deployed about 2,000 Russian peacekeepers to oversee the fragile truce, which analyst Vasadze called "neither war, nor peace."
Ethnic Armenian separatists in Nagorno-Karabakh broke away from Azerbaijan when the Soviet Union collapsed in 1991. The ensuing conflict claimed around 30,000 lives.