Azerbaijan accused Armenia of killing 21 people and wounding dozens in a missile strike near Nagorno-Karabakh on Wednesday, the deadliest reported attack on civilians in a month of fighting over the disputed region.
Armenia immediately denied carrying out the attack, the second in two days that Azerbaijan says killed civilians in the Barda district close to the frontline.
Yerevan also accused Azerbaijani forces of deadly new strikes on civilian areas of Karabakh, as both sides claim the other is targeting civilians after weeks of fierce frontline clashes.
The latest attacks came despite a US-brokered truce agreed at the weekend, the third ceasefire attempt in a row to collapse just minutes after it took effect.
On Wednesday evening, Russian Foreign Minister Sergei Lavrov and his French counterpart Jean-Yves le Drian discussed the raging conflict and said it was important that the warring sides show the necessary "political will" and halt the fighting, Moscow said.
The current clashes broke out on September 27 and fighting has persisted despite repeated attempts to bring about a ceasefire by Russia, France and the United States.
The three countries form the "Minsk Group", which has failed since the 1990s to bring about a negotiated settlement to the conflict.
Officials had earlier said that a new round of Minsk Group talks would take place in Geneva on Thursday.
The International Committee of the Red Cross said Wednesday that an Azerbaijani volunteer and father of two had been killed in the recent flare-up of bombardments and two others wounded.
It was "unacceptable" for both sides to strike urban areas, the organisation tweeted, warning that the conflict "risks spiralling out of control" and is killing civilians "at an alarming rate".
- Shattered storefronts -
Earlier Wednesday Azerbaijani presidential aide Hikmet Hajiyev said Armenian forces had fired Smerch missiles against Barda, accusing them of using cluster munitions "to inflict excessive casualties among civilians".
The prosecutor general's office said the strike had hit a densely populated area and a shopping district, killing 21 civilians and wounding at least 70.
An AFP journalist in the town of Barda saw a row of shattered storefronts, the debris scattered over boxes of fruit and vegetables, and blood pooled on the ground.
Residents gathered to survey the damage to the shops and the burnt-out shells of several cars nearby.
Azerbaijan had on Tuesday accused Armenia of another missile strike in the Barda district that killed five civilians including a two-year-old girl.
The casualties are the worst for Azerbaijani civilians since 13 people were killed in shelling on the country's second city Ganja on October 17.
Armenia has denied carrying out attacks on civilians and on Wednesday defence ministry spokeswoman Shushan Stepanyan said the latest claim was "groundless and false".
Its government said Azerbaijan had hit the Karabakh town of Shusha with rockets on Wednesday, killing one civilian, and a maternity hospital in the region's main city Stepanakert.
Karabakh's rights ombudsman Artak Beglaryan said there were "heavy casualties" in the attacks.
Azerbaijan and Armenia have been locked in a bitter conflict over Karabakh since Armenian separatists backed by Yerevan seized control of the mountainous province in a 1990s war that left 30,000 people dead.
Karabakh's self-declared independence has not been recognised internationally, even by Armenia, and it remains a part of Azerbaijan under international law.
- 'Meaningless meetings' -
A new ceasefire agreement was reached in Washington for a ceasefire to start on Monday but it quickly fell apart.
On Tuesday, Azerbaijani President Ilham Aliyev said he was not against the new round of talks in Geneva but appeared to downplay their significance.
"There have been a lot of meaningless meetings over the past 28 years," he said.
This year's fighting is the heaviest since a 1994 ceasefire, raising fears that both Russia, which has a military alliance with Armenia, and Azerbaijan's ally Turkey could be further drawn into the conflict.
Ankara has been accused of supplying Syrian fighters as mercenaries to bolster Baku's forces.
Azerbaijan has claimed to be making significant gains since the fighting began by retaking areas it lost in the 1990s war, in particular in a buffer zone outside Karabakh seized by the Armenians.
Armenia has admitted to suffering losses and called on volunteers to join the fighting.
More than 1,000 people have been reported dead in the fighting, mainly Armenian separatist fighters but also dozens of civilians on both sides.
Azerbaijan has not released any figures on its military casualties and the death toll is believed to be higher, with Russian President Vladimir Putin saying last week that close to 5,000 people had been killed.