Ethiopia’s air force bombed arms depots and destroyed military hardware in the northern Tigray region on Friday, the prime minister said, escalating a war he launched this week against his former ruling coalition allies. The air strikes in and around the regional capital Mekelle wiped out rocket launchers and other weaponry belonging to the Tigray People’s Liberation Front (TPLF), Prime Minister Abiy Ahmed said in a statement he read on national television. Hours earlier, Abiy - who won last year’s Nobel Peace Prize - justified his decision to start military action in Tigray by saying it was necessary to disarm the TPLF. The campaign had “clear, limited and achievable objectives”, he said. The government is mobilising troops from around the country and sending them to Tigray after two days of clashes between federal forces and the TPLF, Ethiopia’s dominant political force for decades until Abiy took office in 2018. Abiy has called retired generals back to duty in hopes of preventing the military from fragmenting along ethnic lines, a diplomat and a regional security expert told Reuters. The military operations seek “to restore the rule of law and the constitutional order, and to safeguard the rights of Ethiopians to lead a peaceful life wherever they are in the country,” Abiy said. TPLF officials were not immediately available for comment. The government cut phone and internet communications in the region on Wednesday. In a statement, Abiy’s office accused TPLF leaders of hiding in the regional capital Mekelle and “using the civilian population as human shields”. “Members of the TPLF, who ruled the country for the previous 27 years through means of oppression rather than law, have been fugitives from justice,” it said. NOBEL PRIZE, ETHNIC VIOLENCE Abiy took office pledging to open up one of the most restrictive political systems in Africa, and won the Nobel Prize for ending a conflict with neighbouring Eritrea. But ethnic violence has exploded in many parts of the country on his watch, forcing hundreds of thousands of people to flee their homes. Tensions between the federal government and the TPLF have been building for months. The TPLF led a guerrilla movement that came to power in a revolution in 1991, and established a multi-ethnic coalition that was dominated by Tigrayans for decades. Tigrayans have complained of persecution under Abiy, an ethnic Oromo, who ordered the arrest of dozens of former senior military and political officials from the TPLF in a crackdown on corruption. Last year, Abiy reorganised the ruling coalition into a single party which the TPLF refused to join. Diplomats tried to push the sides towards negotiations this week to prevent a civil war. “The stability of Ethiopia is important for the entire Horn of Africa region. I call for an immediate de-escalation of tensions and a peaceful resolution to the dispute,” U.N. Secretary-General António Guterres said in a message on Twitter late on Thursday. Sporadic sounds of shelling were heard from Abdurafi town, near the border between Tigray and the neighbouring Amhara region, at 3 a.m local time (0000 GMT) on Friday, a humanitarian worker in the area told Reuters. Tigray hosts Ethiopia’s largest military base and more than half of the army’s troops. The Tigray regional administration said this week that it had taken over assets of the national defence force’s northern command based in Tigray. Two diplomats and a regional military officer said the claim was credible. The conflict “could test the national military’s cohesion,” the International Crisis Group think tank said in a statement. Federal troops are being helped by local forces from Amhara, its regional president, said in a statement on Thursday. Amhara borders Tigray and the regions are locked in a boundary dispute.