ADDIS ABABA, Ethiopia (AP) — Ethiopia’s prime minister ordered the military to confront a regional government after he says it attacked a military base overnight, citing months of “provocation and incitement” and declaring that “the last red line has been crossed.”

The statement by Prime Minister Abiy Ahmed’s office Wednesday morning, and the reported attack, immediately raised concerns that one of Africa’s most populous and powerful countries could plunge back into war.

The Tigray People’s Liberation Front had played a major role in Ethiopia’s governing coalition before Abiy took office in 2018 and announced sweeping political reforms that won him the Nobel Peace Prize last year. Those reforms, however, have opened space for old grievances.

There was no immediate word from the TPLF, and all internet and phone lines were cut in the northern Tigray region following the announcement. On Sunday, a senior TPLF official, Getachew Reda, told The Associated Press his side will not accept a negotiation with the federal government.

“What we need now is a national dialogue, not a negotiation,” he said, adding that efforts by outside bodies are not bearing fruit so far. The TPLF says the release of detained former officials is one precondition to open talks.

The TPLF has shown increasing signs of discontent, and in September people in Tigray voted in a local election, defying the federal government and increasing political tensions. Tigray officials warned at the time that an intervention by the federal government would amount to a “declaration of war.”

Tigray officials have objected to the postponement of Ethiopia’s national election, once set for August, because of the coronavirus pandemic and the extension of Abiy’s time in office.

Abiy’s statement asserts that the TPLF attacked a military base in Tigray in the early hours Wednesday and attempted to take artillery and other equipment. The statement accused the TPLF of arming and organizing irregular militias in the past few weeks.

The attack “ has been premised on TPLF viewing the Ethiopian National Defense Forces as a foreign army,” the statement says.

The prime minister’s statement adds that after months of “extreme patience” by the federal government, “a war however cannot be prevented only on the goodwill and decision of one side. ... The last red line has been crossed with this morning’s attacks and the federal government is therefore forced into a military confrontation.”