Ethiopia’s dispute with the northern Tigray region escalated Thursday with reports of heavy shelling and the army’s deputy chief declaring that the country had entered into “an unexpected war” and was sending more troops to the area.

The intensifying conflict drew an urgent international response, with the United Nations dispatching a special envoy to Ethiopia’s capital, Addis Ababa, and the International Crisis Group warning that the conflict could spread beyond Ethiopia’s borders.

“Our country has entered into an unexpected war. The war will not come to the center. It will end there,” in Tigray, the deputy chief of the Ethiopian National Defense Force, Birhanu Jula, said on state television.

A statement attributed to the regional government on Tigray TV claimed government fighter jets had bombed the outskirts of the region’s capital, Mekele, but those reports could not be confirmed. Communications, including Internet and phone connections, were cut in the region this week.

Ethiopia’s government has not commented on the bombing allegations, and a spokeswoman for Prime Minister Abiy Ahmed did not respond to a request for comment.

Clashes erupted in Tigray on Wednesday after Abiy, the 2019 Nobel Peace Prize winner, sent troops into Tigray province and declared a “military confrontation” after the regional government attacked a federal military base. Abiy accused the Tigray People’s Liberation Front (TPLF), which for decades was the dominant political force in the country’s multiethnic ruling coalition, of attempting to steal artillery and other military equipment during the attack.

A senior State Department official, who spoke on the condition of anonymity to comment frankly on the volatile conflict, said he had heard “wildly contradictory” reports about events on the ground in Tigray. He said he had heard of military casualties but said that communication networks had been cut and that it was difficult to confirm reports.

The official confirmed that international efforts to de-escalate tensions were underway and said that the United States wanted to be “as helpful as possible to promote a peaceful resolution.”

The official pushed back at suggestions that Ethiopia was engaged in a war, saying that “it is not one sovereign state fighting against another sovereign state.”

Debretsion Gebremichael, president of the Tigray region, told reporters that “we are in position to defend ourselves from enemies that waged war on the Tigray region. . . . We are ready to be martyrs.”

Human Rights Watch called on Abiy’s government to immediately restore communications to the region, saying it hampered critical reporting of events affecting people’s health and safety in Tigray.

“It also undermines their rights to question the government’s account of events,” Mausi Segun, Africa director at Human Rights Watch, said in a statement.

Wroughton reported from Cape Town, South Africa. Morello reported from Washington.