CNN  — 

Ethiopian Prime Minister Abiy Ahmed said Friday that ongoing military operations in the country’s north that have stoked fears of civil war “have clear, limited & achievable objectives.”

Abiy has ordered troops into the restive Tigray region, a move he said was in response to an alleged attack by the Tigray People’s Liberation Front (TPLF) on a federal military base in the regional capital of Mekelle.

Taking to Twitter, Abiy accused the TPLF of “criminal hubris & intransigence,” claiming they rejected the federal government’s efforts at “mediation, reconciliation, dialogue.”

“Ethiopia has no place for criminal elements,” he added in a later tweet.

He justified the military action by citing an article of the country’s constitution that stipulates that the federal government “safeguards and defends the Constitution.”

The acting President of Tigray, Debretsion Gebremichael, blames the federal government for the current escalation, saying the region is acting in self-defense.

Meanwhile, neighboring Sudan announced Thursday that it was closing its border with Ethiopia – along a part of which Tigray sits – citing “security tensions.”

Ethiopia’s federal government has announced a six-month state of emergency in Tigray, which gives it broad security powers. Internet and communications lines have been blacked out in the region, according to local reporters.

Details of the fighting have been difficult to confirm because of this.

On Thursday, the country’s military said it was at “war” with the ruling party of the Tigray region.

The current round of tensions in Tigray started in August when Abiy’s government delayed scheduled elections, saying the risk of Covid-19 was too high.

Officials in Tigray cried foul and held their own election in September anyway, with more than two million people turning out to vote.

In retaliation, the federal government withheld funding from the TPLF leadership in Mekelle, promising to send it directly to local leaders instead. This set off a tit-for-tat series of recriminations and rhetoric between the regional and federal governments that has been steadily building.

Foreign observers and diplomats are increasingly worried that the situation could significantly escalate within Tigray and beyond.

The United Nations Secretary-General, António Guterres, said he was “deeply alarmed” by the situation.

“The stability of Ethiopia is important for the entire Horn of Africa region,” he said in a tweet early Friday morning. “I call for an immediate de-escalation of tensions and a peaceful resolution to the dispute.”

Military escalation is “opening a dangerous path for the stability of the country and the entire region,” the European Union’s high representative for foreign affairs and security, Josep Borrell Fontelles, wrote in a tweet Wednesday.

Ethiopia has received hundreds of millions of dollars in US aid and military assistance and has been a key ally of the US in combating extremist groups in neighboring Somalia.

CNN’s David McKenzie and Brent Swails contributed to this report.