Ethiopian government forces have been systematically raping and abusing hundreds of women and girls in the current conflict in Tigray, according to a new report from Amnesty International.

Adding to a growing body of evidence that rape is being used as a weapon of war in the northern region of Ethiopia, Amnesty’s research offers a snapshot of the extent of the crimes in an area where communications with the outside world have been deliberately restricted by federal authorities.

The report comes as Ethiopia’s government this week called on “all capable Ethiopians” to join the military to stop resurgent forces from the Tigray region “once and for all”, in an apparent abandonment of its unilateral ceasefire in June.

The war in Africa’s second-most populous country has risked destabilising the Horn of Africa region since it broke out in November, when the prime minister, Abiy Ahmed, a Nobel peace laureate, declared war on the regional government, controlled by the Tigray People’s Liberation Front, which had ruled Ethiopia for almost 30 years.

The report, based on the accounts of 63 Tigrayan women and medical professionals, details how women have been routinely subjected to mutilation, gang rape, sexual slavery and other forms of torture by members of Ethiopia’s army, the Ethiopian National Defence Force; the Eritrean Defence Forces, which are allied to Ahmed’s government; and Amharan militia fighters as the Tigray conflict continues, said Amnesty.

The presence of Eritrean troops, and an Amharan militia group called Fano, fighting against the TPLF forces, has caused outrage and brought international sanctions. According to researchers at Belgium’s University of Ghent, there have been at least 10,000 reported deaths and 230 massacres. Thousands have suffered horrific abuses, according to the UN.

Agnes Callamard, Amnesty International’s secretary general, said: “The severity and scale of the sexual crimes committed are particularly shocking, amounting to war crimes and possible crimes against humanity. It makes a mockery of the central tenets of humanity.

“It’s clear that rape and sexual violence have been used as a weapon of war to inflict lasting physical and psychological damage on women and girls in Tigray. Hundreds have been subjected to brutal treatment aimed at degrading and dehumanising them.”

She said the Ethiopian government must take immediate action and called on the African Union and UN to bring an end to the conflict.

Rights groups and aid organisations, whose activities have been restricted, must be granted access, she added.

Twelve of the women interviewed by Amnesty said they had been raped by soldiers in front of their family members, including children. Five of the women were pregnant at the time.

In one account, a 20-year-old woman, referred to as Lena*, told Amnesty she was attacked in her home in November last year. Three armed men who spoke Amharic and wore a mixture of military uniforms and civilian clothing raped and threatened to kill her, she said.

“I did not scream; they gestured to me not to make any noise or they would kill me. They raped me one after the other … I was four months pregnant. I don’t know if they realised I was pregnant – I don’t know if they realised I was a person,” she told Amnesty.

A 35-year-old mother with two children, referred to as Nigist*, said she and four other women were raped by Eritrean soldiers in Sheraro on 21 November.

“Three of them raped me in front of my child. There was an eight-months pregnant lady with us, they raped her too,” she said. “They raped the women and slaughtered the men.”

Amnesty said Tigrayan health facilities recorded 1,288 cases of gender-based violence between February and April. Many of the women interviewed for the report said they had not visited clinics.

In May, a nun in Tigray told the Guardian that rape by security forces was occurring daily.

“Rape is starting at the age of 8 and to the age of 72,” she said. “It is so widespread, I go on seeing it everywhere, thousands. This rape is in public, in front of family, husbands, in front of everyone. Their legs and their hands are cut, all in the same way.”

TPLF forces have also been accused of potential war crimes during a conflict where historic and ethnic divisions have intensified. Ahmed has repeatedly said that any crimes would be investigated.

Despite Ethiopia announcing early victories, it was forced to declare a ceasefire in June as resurgent Tigrayan forces retook much of the region. TPLF forces have since marched on the neighbouring Afar and Amhara regions. Ethiopia’s government has vowed to summon its “entire defensive capability” against Tigray.

The conflict has led to a hunger crisis, with more than 400,000 people facing famine conditions. Nearly 70,000 people have fled to neighbouring Sudan.