Fears are growing of civil conflict in the east African country.

Ethiopian PM Abiy Ahmed earlier rejected a request for peace talks from the Tigray authorities.

Hundreds have been killed in eight days of fighting between Tigray forces and the federal army.

Ethnic divisions have been rising in Ethiopia as some communities express their increased desire for self-government.

Once the country's most powerful party, the Tigray People's Liberation Front (TPLF) that rule the Tigray region has been feuding with Prime Minister Abiy since he came to power in 2018 and promised reform nationwide.

Most recently, the TPLF defied a national ban on elections due to coronavirus. Mr Abiy responded by calling their vote illegal.

Last Wednesday, Mr Abiy ordered a military offensive after an army base in the Tigrayan capital, Mekelle, was taken over by forces loyal to the regional government of Tigray.

The Tigray People's Liberation Front (TPLF) declared a state of emergency to "defend the security and existence of the people of Tigray and their sovereignty", the state broadcaster Tigray TV reported.

It relayed a government warning that "action will be taken against anyone who fails to co-operate".

The regional authorities also repeated the accusation that neighbouring Eritrea was involved in the conflict, something both Eritrea and the federal government have denied.

The federal authorities insist their fight is against the regional government - not the Tigrayan people.

Mary Harper, BBC World Service Africa editor

This is dramatic language from the Tigrayan regional leadership. But it matches that coming from the federal authorities, who have vowed to keep fighting until what they describe as the "criminal junta" running Tigray has been "crushed".

There has been a lot of talk of Ethiopia slipping towards civil war, with international bodies calling for a ceasefire and a negotiated way out of this crisis.

But many Ethiopians, especially those in Tigray, say their country has already sunk into war.

Thousands are fleeing a country that has been a beacon of relative stability in the crisis-prone Horn of Africa.

With both sides sticking stubbornly to war talk and little indication of any common ground for potential comprise, the fear is that the fighting will continue,

Ethiopia's neighbours will be sucked in, and civilians, many of whom are already living in precarious conditions, will be those who pay the heaviest price.

In other developments:

The TPLF was the most powerful member of Ethiopia's ruling coalition for many years but Mr Abiy curbed its influence after winning power in 2018 on the back of anti-government protests.

Relations got worse last year after Mr Abiy - who won the 2019 Nobel Peace Prize for ending a two-decade conflict with - dissolved the ruling coalition, which was made up of several ethnically based regional parties.

He merged them into a single, national party, the Prosperity Party, which the TPLF refused to join.

Tigrayan leaders say they have been unfairly targeted by purges and allegations of corruption, and say Mr Abiy is an illegitimate leader, because his mandate ran out when he postponed national elections due to the coronavirus pandemic.

The simmering row boiled over in September after the TPLF defied the nationwide ban on elections, and held a vote which was declared illegal by the central government.