The announcement came after the Tigray rebels claimed to have captured several towns in recent days and said they were considering marching on capital Addis Ababa.
Ethiopia's cabinet has declared a nationwide state of emergency after forces from the northern region of Tigray said they were gaining territory and considering marching on the capital Addis Ababa.
"The state of emergency is aimed to protect civilians from atrocities being committed by the terrorist TPLF group in several parts of the country," Fana Broadcasting Corporate reported, referring to the Tigray People's Liberation Front.
The announcement on state-affiliated media came two days after Prime Minister Abiy Ahmed urged citizens to take up arms to defend themselves from the TPLF group.
Earlier on Tuesday, authorities in Addis Ababa told residents to register their arms and prepare to defend their neighbourhoods.
"All residents must be organised by blocks and neighbourhoods to protect peace and security in their home area in coordination with security forces, who will coordinate activities with community police and law enforcers," said Kenea Yadeta, chief of the city's Peace and Security Administration Bureau.
"There will be recruitment and organising of the city's youth to work in coordination with security forces to protect peace and security in their area," Kenea said in remarks carried by state media.
Disputed territorial gains
House-to-house searches were being conducted and troublemakers arrested, said a statement carried by the Ethiopian News Agency on Tuesday.
The governments of four of the country's 10 regions also called upon Ethiopians to mobilise to fight against the Tigrayan forces, state-affiliated Fana TV said.
TPLF has in recent days claimed control of two key cities about 400 kilometres (250 miles) from Addis Ababa.
The government has denied claims of TPLF territorial gains which, if confirmed, would represent a major strategic advance for the rebels in the year-long war.
Abiy sent troops into Tigray in November 2020 in response to what he said were attacks on army camps by the TPLF, and promised a swift victory.
But by late June the rebels had regrouped and retaken most of Tigray, and fighting spread to the neighbouring regions of Afar and Amhara.
The latest fighting has been in Amhara over the cities of Dessie and Kombolcha, which lie at a strategic crossroads on the main highway to Addis Ababa.
The international community has expressed alarm at the expanding conflict, and called again for an immediate ceasefire and for the African Union to broker peace talks between the warring parties.
The United States on Tuesday warned Tigrayan rebels against advancing on Addis Ababa after gains north of the Ethiopian capital, urging talks instead.
"Let me be clear: We oppose any TPLF move to Addis or any TPLF move to besiege Addis," Jeffrey Feltman, the US special envoy for the Horn of Africa, said at the US Institute of Peace, referring to the Tigray People's Liberation Front.