Armenia on Sunday accused Azerbaijan of violating a fresh humanitarian truce aimed at halting weeks of fighting over the Nagorno-Karabakh region that has claimed hundreds of lives.
Yerevan's defence ministry spokeswoman Shushan Stepanyan said on Twitter that Azerbaijan had fired artillery shells and rockets in the early hours of Sunday, just minutes after the ceasefire went into effect from midnight.
There was no immediate reaction from Azerbaijan.
Saturday's ceasefire followed a major escalation that saw a missile strike kill 13 people including small children in the Azerbaijani city of Ganja, for which President Ilham Aliyev vowed to take "revenge".
A previous truce brokered by Russia to allow the warring sides to exchange prisoners and bodies and begin "substantive" talks quickly broke down, with both sides accused each other of violations.
Azerbaijan and the Armenian separatists who control its Karabakh region have been locked in a bitter impasse over the fate of the mountainous province since a war in the 1990s that left 30,000 people dead.
Clashes erupted again three weeks ago and have killed at least 700 people, threatened to draw in regional powers Russia and Turkey, and raised alarm over the failure of a decades-long international mediation.
The real death toll is probably much higher since Azerbaijan has not published fatalities among its soldiers.
The EU on Saturday condemned the strikes on Ganja and said the original ceasefire deal "must be fully respected without delay".
"All targeting of civilians and civilian installations by either party must stop," said a spokesperson for EU foreign affairs chief Josep Borrell.
Turkey, a staunch ally of Azerbaijan and widely accused of supplying mercenaries to bolster Baku's forces, said the strikes were a war crime and called on the international community to denounce them. (AFP)