Indiscriminate shellfire by Turkish troops – and to a lesser extent Kurdish forces – has killed scores of civilians in Syria, a human rights group alleges.

Amnesty International said it had verified witness testimony from the north-western Kurdish enclave of Afrin that “painted a grim picture”.

The use of artillery in civilian areas is prohibited by international law.

Turkey has denied targeting civilians since launching an offensive against a Kurdish militia in Afrin last month.

The Turkish government says the People’s Protection Units (YPG) is an extension of the banned Kurdistan Workers’ Party (PKK), which has fought for Kurdish autonomy in south-eastern Turkey for three decades.

The YPG denies any direct organisational links to the PKK – an assertion backed by the US, which has provided the militia and allied Arab fighters with weapons and air support to help them battle the jihadist group Islamic State (IS).

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According to the Kurdish Red Crescent, attacks on Afrin by Turkish-led forces between 22 January and 21 February killed 93 civilians, including 24 children.

Meanwhile, YPG shellfire reportedly killed four civilians in Azaz, including one child.

Amnesty said on Wednesday that it had interviewed 15 people living in, or recently displaced from, towns and villages in Afrin and Azaz. Video analysis had corroborated their accounts of coming under indiscriminate shellfire, it added.

Sido, a resident of the village of Maabatli, described how a shell hit his neighbour’s house on 25 January, killing five of the six people inside.

“The attack destroyed the house completely, killing the father, mother and three children younger than 15. A fourth child… survived but is in critical condition,” he was quoted as saying. “There are no military headquarters next to the house… The closest frontline is 41km away at the border.”

The Turkish military has repeatedly denied targeting or hitting civilians or civilian infrastructure. It says it has “neutralised” more than 2,100 “terrorists” since the start of the offensive on Afrin, which means it has captured or killed them.

Saed, a pharmacist at a psychiatric hospital in Azaz, told Amnesty he believed YPG fighters were behind an attack on the medical facility on 18 January that reportedly killed one female patient and injured 13 others.

“The psychiatric facility is located next to an orphanage and another civilian hospital,” he said. “There is no military presence next to the psychiatric facility and all three buildings are kilometres away from any frontline.”

In addition, a number of missiles and mortar rounds have fallen in residential areas within Turkey, killing at least seven civilians.

The YPG has denied shelling civilians in Syrian areas neighbouring Afrin and Turkish border towns, and accused Turkish security forces of carrying out attacks to justify their offensive.

Last Friday, Human Rights Watch said the Turkish military appeared to have failed to take necessary precautions to avoid harming civilians in three attacks in late January in Afrin, where an estimated 323,000 people live. The attacks killed 26 civilians, including 17 children, it said.

Lynn Maalouf, Amnesty International’s Middle East research director, said: “The use of artillery and other imprecise explosive weapons in civilian areas is prohibited by international humanitarian law and all parties should cease such attacks immediately.”