In early December, Ethiopian state television broadcast something unexpected: a fiery exchange between civilians in Shire, in the northern Tigray region, and Ethiopian soldiers, who had recently arrived in the area. To the surprise of viewers used to wartime propaganda, the Tigrayan elders spoke in vivid detail of the horrors that had befallen the town since the outbreak of war between the federal government of Prime Minister Abiy Ahmed and the Tigray People’s Liberation Front (TPLF), the region’s longstanding ruling party, which was ousted from the state capital of Mekelle in late November. Residents had been “slaughtered like chicken”, the elders said, their corpses abandoned to be “eaten by hyenas”. They also spoke of rampant looting and vandalism: “All government assets have been destroyed and looted,” said one. Perhaps most revealing, however, was the implication that those responsible for the carnage were not Ethiopian federal troops, but outsiders. “You need to solve this problem immediately,” said an elder addressing the generals and newly appointed Tigray president, Mulu Nega. “How can institutions that should serve the government of the day be allowed to be destroyed and looted by hooligans who do not have Ethiopian values in them?” Thousands are thought to have been killed, civilians among them, and nearly 50,000 people have fled to Sudan since Ethiopia’s Tigray war began on 4 November. Pitched battles involving tanks and fighter jets – as well as militia from Amhara, which borders Tigray to the south – have flattened villages and emptied towns. But according to eyewitnesses, aid workers and diplomats, the fighting has also involved many thousands of soldiers from neighbouring Eritrea, suggesting that what the Ethiopian government calls a “law enforcement operation” bears the hallmarks of a regional conflict. Abiy and Eritrea’s president, Isaias Afwerki, share a common enemy in the TPLF, which dominated Ethiopia’s federal government for nearly three decades before Abiy took office in 2018. Ethiopia and Eritrea fought a bloody war between 1998 and 2000, which claimed an estimated 100,000 lives. Earlier this month the former president of Tigray, Debretsion Gebremichael, accused Eritrean forces of mass looting. Before that he alleged Tigrayan forces were fending off Eritrean divisions on several fronts. The TPLF has claimed responsibility for one of three missile strikes on Eritrea since the war began, arguing it had acted in self-defence since the airport in Asmara, the capital, which was hit by at least two rockets in the strike, had been used to launch attacks. Refugees crossing into Sudan have also made similar claims, telling reporters and aid workers that artillery shells that hit towns in western Tigray had come from Eritrea. But confirmation has been complicated by the lack of access for outsiders, including media, and the cutting off of communications to the region. Phone lines were restored in parts of Tigray this month, but there is still no internet. Abiy has denied all allegations, and told the UN secretary-general, António Guterres, on 9 December that he could guarantee no Eritrean troops had entered Ethiopian territory. However, his government does acknowledge that Ethiopian troops who escaped to Eritrea at the start of the war were aided by Eritreans who fed, clothed and armed them before they returned to the fight in Tigray. “The Eritrean people are not only our brothers,” Abiy told parliament last month. “They have also shown us practically that they are friends who stood by our side on a tough day.” But diplomatic sources have backed accusations that Eritrean soldiers have been actively involved in combat inside Tigray. Reuters, which interviewed several unidentified diplomats in the region and a US official, revealed earlier this month that the US government believed Eritrean soldiers had crossed into Ethiopian territory in mid-November via three northern border towns: Zalambessa, Rama and Badme. A spokesperson for the US state department later confirmed the details, marking a shift among US officials, who have previously praised Eritrea for its “restraint”. “We are aware of credible reports of Eritrean military involvement in Tigray and view this as a grave development,” said the spokesperson. “We urge that any such troops be withdrawn immediately.” “In the lingo of the state department that means they have intercepts, satellites and maybe even human intelligence as well,” a top EU diplomat in the region told the Guardian. “From everything we’ve been told it is incontrovertible they [Eritrean troops] are involved. It’s absolutely clear.” Mesfin Hagos, a former Eritrean defence minister turned opposition figure, said in an article for online publication African Arguments, that Isaias had deployed four mechanised divisions, seven infantry divisions and a commando brigade, citing sources in the defence ministry among others. Wallelegn, a Tigrayan working in Shire when the war began who later escaped to the Ethiopian capital, Addis Ababa, told the Guardian that the “Eritreans were really leading the Ethiopian forces in the area”. “Their uniform is different and they are relatively old and skinny compared with the Ethiopian defence forces,” he said. “In the early days of their arrival to Shire they were looting, randomly shooting, mainly youngsters, and burning factories.” He added: “At first the Ethiopian forces were emotional, and were not doing much to stop the attacks. But later on they started to take charge [and impose order].” Tigray is also home to around 100,000 refugees from Eritrea, many of whom have fled indefinite national service and military conscription. When the war began they were caught in the middle and cut off from relief supplies. A humanitarian worker in Shire told the Guardian that many refugees in Hitsats camp fled as soon as troops from Eritrea arrived in the vicinity on 19 November. According to the source, the approaching “north force” – a reference to Eritrean troops crossing the border from the north – armed refugees before looting property, slaughtering livestock and burning crops. A senior UN official told the Guardian they had received similar allegations, including of the killing of three security guards employed by the UN at Hitsats camp who tried to prevent the abduction of refugees, and the forced conscription of refugees to fight alongside the Eritrean army. On 11 December, the head of the UN refugee agency said it had received an “overwhelming” number of reports of Eritrean refugees in Tigray being killed, abducted or forcibly returned to Eritrea over the past month. That same day Ethiopian authorities started putting Eritrean refugees in Addis Ababa on buses and returning them to Tigray against their will. The Ethiopian government said it was “safely returning” refugees to camps where there would be access to “service delivery systems” in order to process their cases. In recent days, according to a refugee based in Adi Harush camp, south of Hitsats, Eritrean soldiers accompanied by Ethiopian troops have patrolled the camp on the hunt for individuals. “They were searching name-by-name and home-to-home. Their main target seems to be opposition members,” said the refugee, who asked for anonymity for fear of reprisals. Eritrean state television, the only broadcast media in the country, has made no mention of the conflict in Ethiopia since it began, Eritreans living in Asmara say. President Isaias has not uttered a word in public in response to the missiles fired at Asmara last month. Nor has his minister of information, Yemane Gebremeskel, whose office building narrowly escaped a rocket strike on 13 November. Eritrea’s foreign minister, Osman Saleh Mohammed, acknowledged the war but denied any involvement. “We are not part of the conflict,” he told Reuters last month. Ethiopian officials, meanwhile, have accused the TPLF of manufacturing fake Eritrean uniforms to falsely implicate their neighbours, and insist that the conflict remains an exclusively internal affair. Meron Estefanos, director of the Eritrean Initiative on Refugee Rights, notes that not all allegations involving Eritreans are plausible. She told the Guardian that while some refugees and prominent opposition figures living in Ethiopia had certainly been forcibly returned to Eritrea, estimates of several thousand abductees are improbable. But as for the broader claims of Eritrean involvement, she said: “People inside Eritrea know exactly what is going on. “I am sick and tired of the fact that, no matter how many Eritreans say that Eritrean troops are in Tigray, it is not confirmed until a foreign diplomat says it is.”