Azerbaijan has accused Armenia of attacking its cities overnight in violation of a ceasefire less than a day old.
Nine civilians were killed and 30 wounded when missiles fired at Ganja, Azerbaijan’s second-biggest city, hit a residential building, authorities said.
Another city, Mingachevir, was also attacked by missiles, according to the prosecutor general’s office.
Armenian officials in the Nagorno-Karabakh region denied the claims and said it was sticking to the Russia-brokered truce deal, which came into force noon on Saturday.
They made counter-claims that Azerbaijani forces had shelled Stepanakert overnight, the region’s capital, and other towns.
A boy runs past a damaged store after reports of a rocket attack on Ganja
Fighting had been going on since 27 September over disputed Nagorno-Karabakh.
It lies in Azerbaijan but is populated and ruled by ethnic Armenians who shun the Azeri government.
It is the biggest flare-up in the conflict since a separatist war ended in 1994.
The reports of fighting come hours after foreign ministers from the two countries signed a truce in Moscow following the intervention of Russian President Vladimir Putin.
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Kim Kardashian West donates $1m to Armenia Fund
The deal said the ceasefire should lead to talks on settling the conflict.
On Sunday morning, the situation was “relatively calm”, according to Nagorno-Karabakh leader Arayik Harutyunyan, with just a few “skirmishes”.
However, he said it was unclear how long the lull in fighting would last.
“There is no shelling of our towns and villages. At the front line, there is some shooting with the use of artillery. There are some skirmishes on the border,” Mr Harutyunyan said.
“Since the morning, it seems calm, but within minutes the situation can change.”
Arayik Harutyunyan, leader of Nagorno-Karabakh, said the situation was relatively calm on Sunday morning
Nagorno-Karabakh’s foreign ministry said on Saturday that the only way for lasting peace was for the international community to recognise it as an independent republic.
Azerbaijan’s president said in an interview with the Russian RBC news outlet that “if the Armenian side is committed to the cease-fire regime… the phase of political settlement will begin.”
Kim Kardashian West, meanwhile, has said she is donating $1m to the Armenia Fund to help people caught up in the fighting.
The reality TV star and social media celebrity has Armenian heritage.