Ethiopia's parliament has voted to dissolve the government of the northern Tigray region, amid a dispute which has escalated into armed conflict.
In an emergency session, parliament declared the Tigray administration illegal and voted to replace it.
On Friday, Prime Minister Abiy Ahmed said air strikes had been carried out on military targets in Tigray.
There are fears the conflict could lead to civil war, which could also destabilise neighbouring countries.
The leaders of Tigray dominated Ethiopia for many years until Mr Abiy came to power in 2018 on the back of anti-government protests and curbed their influence.
They 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 elections due to coronavirus.
The UN has called for a "de-escalation in the fighting".
What did parliament say?
The House of Federation - one of Ethiopia's parliamentary chambers - said the Tigray leadership had "violated the constitution and endangered the constitutional system", according to the state-owned broadcaster EBC.
It said a new caretaker administration would hold elections and "implement decisions passed on by the federal government".
The simmering row boiled over in September after Tigray's ruling party, the Tigray People's Liberation Front (TPLF), defied the nationwide ban on elections, and held a vote which was declared illegal by the central government.
Military conflict may not be over quickly
By Kalkidan Yibeltal, BBC News, Addis Ababa
Parliament's move signals that the crisis is deepening even though international calls for restraint and de-escalation are increasing.
In a tweet on Saturday, Prime Minister Abiy Ahmed said the military operation he ordered in the state "aims to end the impunity that has prevailed for far too long" and "to hold accountable individuals and groups under the laws of the land".
For its part, the TPLF, in a statement posted on Facebook, said that "through their capacity and in the just war they are engaged in, the Tigray people will win".
Such statements suggest solving the crisis without further military confrontation is increasingly becoming unlikely.
Both the TPLF and the federal government say they will win the conflict in a short period of time but that might not happen.
Prime Minister Abiy has said that there were airstrikes on Friday to destroy missiles, radar equipment and rockets, and that these will continue. The TPLF respond that they have modern weapons.
So, it appears that the conflict is intensifying and it's possible that it might spill over to other parts of the country - and the region.
What's the latest on the fighting?
It's hard to get much detail because the internet and phone lines to Tigray have been cut and the national government is not saying much.
But there are reports that the fighting is spreading along Tigray's border with the Amhara region, which is backing the federal government. There have also been reports of clashes near the border with Eritrea and Sudan, which has partially closed its frontier with Ethiopia.
While Mr Abiy said various military targets had been destroyed, officials in Tigray have denied to the BBC that an air attack took place on Friday.
In a statement earlier on Friday, Mr Abiy, who won the 2019 Nobel Peace Prize for helping to end a long-standing conflict with Eritrea, insisted that the military operation in Tigray had "clear, limited and achievable objectives".
He previously declared a six-month state of emergency in the region and gave a new military taskforce the powers to "restore law and order".
Tigrayan leader Debretsion Gebremichael previously accused Mr Abiy's administration of plotting to invade the state.
What's this all about?
Tension has been mounting for some time as relations between the TPLF and the federal government have deteriorated.
Although Tigray represents just 6% of Ethiopia's population of more than 100 million, the TPLF used to be the dominant force in Ethiopia's ruling coalition but its power has waned since Mr Abiy became prime minister.
Last year, he dissolved the ruling coalition, made up of several ethnically-based regional parties, and merged them into a single, national party, the Prosperity Party, which the TPLF refused to join.
A statement from the prime minister's office on Friday said that some members of the TPLF were "fugitives from justice" and suggested they opposed Mr Abiy's attempts to reform the way Ethiopia was run.
This week, after TPLF leaders accused the government of preparing to invade, they seized a federal army base in Tigray's capital, Mekelle, prompting Mr Abiy to mobilise the army.