Tigray rebels in Ethiopia announced Thursday they were in full-blown war with the federal government as heavy artillery attacks were reported in neighboring states, according to Agence France-Presse (AFP)

The announcement and renewed fighting effectively shatters a peace pact that ended a devastating two-year war in 2022, with rebel forces mobilizing for an armed struggle they hope will lead to the removal of the federal prime minister.

Tensions have been rising for months between the federal government and authorities in northern Tigray state, which fought a devastating civil war in 2020-22 that killed more than 600,000, according to African Union estimates.

The two sides accuse each other of triggering renewed conflict with attacks this week, and the fighting could draw neighboring Eritrea into a wider conflict.

On Wednesday, the Tigray People's Liberation Front (TPLF), which dominates the state, seized control of three airports from federal police and launched attacks into the neighboring states of Afar and Amhara.

A humanitarian source in Afar told AFP that rebels launched heavy artillery attacks Thursday as they attempted to take control of the town of Yallo, near the Tigray border.

"We are in full-blown war now," Amanuel Assefa, TPLF vice president said.

He confirmed Tigray forces were fighting alongside local armed groups in Afar and Amhara.

Rebels took control of Abala, also on the Tigray-Afar border, Wednesday, according to a foreign security source based in Ethiopia. A TPLF source said it had seized several other Afar towns, but the claim could not be confirmed.

The foreign security source said fighting occurred around the Amhara town of Weldiya – one of the few routes to the capital, Addis Ababa.

Analysts say it mirrors the Tigray strategy during the 2020-22 war – seeking to cut off supply lines and push toward the capital.

"Their stated aim is to take Addis, but their tactical maneuvers to reach the city are not yet known," said Kjetil Tronvoll, a regional expert at Oslo New University College.

The offensive in Afar, he said, likely aims to cut off supplies from Djibouti, which supplies almost all of Ethiopia's international trade cargo, including fuel.

Ethiopian President Taye Atske Selassie Amde, speaking at the U.N. General Assembly Wednesday, decried "the forces of destruction and mayhem" and "interference in our internal affairs by adversarial elements."

Analysts say Tigray rebels have support from Eritrea, which fears landlocked Ethiopia is planning to invade its territory to gain access to the Red Sea.

Assefa told AFP, "We have no information about Eritrea's plans." Asked if they would request Eritrean intervention, he responded, "Not yet."

The Sudanese army is also angry with Ethiopia over its alleged support for its paramilitary enemies, the Rapid Support Forces. Tensions also have occurred with Türkiye, Somalia and Egypt over a range of issues.

The renewed fighting comes at an awkward moment for the U.S., which only this month lifted sanctions and arms embargoes on Ethiopia and Eritrea related to the 2020-22 civil war, saying the "national emergency ... has expired."

The U.S. Embassy sided with Ethiopia's government Wednesday, saying it was "disappointed to see TPLF leadership ... launch a large-scale offensive."

The TPLF is fighting alongside the insurgent group Fano in Amhara. They forged an anti-government alliance with five other armed groups this past weekend.

It shows the changing dynamics from the 2020-22 civil war, when Fano and Eritrea both fought with the government against Tigray forces, only to be frustrated when a peace deal was signed in 2022.

The TPLF ruled Ethiopia from 1991 to 2018 before being sidelined with the rise of Prime Minister Abiy Ahmed, eventually triggering the 2020-22 civil war.

The 2022 Pretoria Peace Agreement maintained an uneasy calm until late last year, when clashes resumed.

The federal government has since launched drone strikes in Tigray and massed troops at the Tigray border.

Rights groups have accused the TPLF of forced recruitment this year as it prepared for renewed conflict, even as about 1 million people remained displaced from the 2020-22 war.