Azerbaijan has accused Armenia of killing 21 people and wounding dozens in a missile attack 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, which Azerbaijan says killed civilians in the Barda district close to the front line.

Yerevan also accused Azerbaijani forces of deadly new attacks on civilian areas of Karabakh, as both sides claim the other is targeting civilians after weeks of fierce front-line 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.

The current clashes broke out on September 27 and fighting has persisted despite repeated attempts to bring about a ceasefire by France, Russia and the United States.

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”.