Ethiopian Prime Minister Abiy Ahmed defended his government’s military campaign against a rebellious regional government in the north as a limited exercise to rout out “criminal elements” Friday, amid mounting international criticism and fears the situation could descend into all-out war.

Abiy insisted that his government’s military offensive against the powerful Tigray People’s Liberation Front (TPLF), which controls the country’s northernmost region of Tigray, had “clear, limited [and] achievable objectives – to restore the rule of law [and] the constitutional order, and to safeguard the rights of Ethiopians to lead a peaceful life”.

“The Federal [government] patiently tried for several months to resolve differences with TPLF leadership peacefully,” Abiy, who won last year’s Nobel Peace Prize for signing a peace deal with neighbouring Eritrea, wrote on Twitter.

“We shall extract the region of these criminal elements [and] relaunch our country on a path to sustainable prosperity for all.”

Abiy’s comments appeared to be a response to growing expressions of concern from the international community over the offensive, which Ethiopia’s deputy chief of defence staff, Birhanu Jula Gelalcha, described to reporters Thursday as a “war”.

READ: Ethiopia Is On the Brink of Civil War

The head of the United Nations, Secretary General António Guterres, said on Twitter late Thursday that he was “deeply alarmed” by the situation.

“The stability of Ethiopia is important for the entire Horn of Africa region,” he wrote, calling for an “immediate de-escalation of tensions”.

Ahmed Soliman, a research fellow at the Chatham House international affairs think-tank, told VICE News that while Abiy’s comments stressing the limited, achievable goals of the offensive appeared to be in part a response to “very clear concerns emanating from the international community”, they didn’t allay concerns of a descent into a protracted and destabilising conflict.

He said that while there were hopes that the worst-case scenario of all-out conflict could be avoided in favour of a negotiated settlement, “there have been a huge number of opportunities to charter a different course up until now, and engage in genuine dialogue – and those have been missed”.

“Both sides have different ambitions, and will want to maximise their position ahead of any potential negotiations,” he said.

Ethiopia was plunged into crisis Wednesday when Abiy announced his government had sent in troops to the restive Tigray region, in response to Tigrayan regional forces allegedly attacking a federal military camp in the region and attempting to loot military equipment.

The government mobilised troops from across the country to Tigray, declared a six-month state of emergency there and cut off internet and phone services, as well as closing the airspace over the region.

While there have been intermittent reports of gunfire and clashes since Wednesday, with Reuters reporting shelling could be heard from the town of Abdurafi early Friday, the communications blackout has made verifying the intensity of clashes and number of casualties difficult.

Debretsion Gebremichael, head of the TPLF and president of the Tigray region, said at a press conference Thursday that fighting was continuing in the west of the province, and the government was amassing federal troops on the borders of the neighbouring Amhara and Afar regions.

“What has been initiated against us is clearly a war, an invasion …. This is a war we’re conducting to preserve our existence,” Debretsion told reporters, insisting his troops were prepared to defend the region, which he pledged would be “a burial place for the reactionaries”.

The military offensive follows long-building tensions between the federal government and the TPLF, who for decades held a dominant position in Ethiopian politics, but have complained of being increasingly sidelined since Abiy came to power in 2018. In 2019, the TPLF quit his ruling coalition, and relations deteriorated further when Tigrayan leaders held regional elections in September in defiance of a federal decision to postpone any voting until after the coronavirus pandemic.

Observers have warned that any war could be protracted and bloody, with the potential to draw in Eritrea, which borders Tigray to the north, and only signed a peace deal with Ethiopia in 2018, ending decades of tensions.

Tigray has a large paramilitary force and well-organised militia, with a total strength of up to 250,000 troops, according to an International Crisis Group briefing, while the TPLF appeared to have strong support from Tigrayans.

Soliman said there were also concerns that the conflict was fuelling rivalries between Tigrayan elites and those from the neighbouring Amhara region, which has dispatched its special forces to fight alongside the federal government in Tigray.

“One of the most concerning aspects of this conflict is the heightening of those ethnic tensions in the longer-term,” he said.