The announcement comes a day after nine rebel groups said they would join forces in an alliance built around the Tigray People's Liberation Front with an aim to "remove the regime".

"There are sacrifices to be made, but those sacrifices will salvage Ethiopia," Abiy Ahmed said on Twitter. (AFP)

Ethiopia must be ready to make "sacrifices" to "salvage" the country, Prime Minister Abiy Ahmed has urged, as fighting in the north intensifies between government forces and Tigrayan rebels who threaten to advance on the capital.

His announcement came on Saturday, a day after nine rebel groups said they would join forces in an alliance built around the Tigray People's Liberation Front (TPLF), which has been locked in a year-long war against Abiy's government.

"There are sacrifices to be made, but those sacrifices will salvage Ethiopia," Abiy tweeted.

"We have seen the tests and obstacles and it made us stronger," he said, adding: "We have more allies than the people who turned their backs on us."

"For us, Ethiopians, dying for our sovereignty, unity and identity, is an honour. There is no Ethiopianism without sacrifice," the government's communication service said on Twitter.

READ MORE: Ethiopia declares nationwide state of emergency

'Remove the regime'

TPLF representative Berhane Gebre-Christos said on Friday the alliance aimed to "remove the regime," as he signed the nine-party agreement in Washington.

Last weekend, the TPLF said it had taken two strategic cities in the region of Amhara, where its fighters had advanced after retaking their Tigray bastion in June.

It said Wednesday it had reached the town of Kemissie in Amhara, 325 kilometres (200 miles) northeast of the capital.

The TPLF added it was running "joint operations" with the Oromo Liberation Army, another rebel group which predicted Addis Ababa could fall in a matter of weeks.

The government, which on Tuesday declared a nationwide emergency, has denied any major rebel advance or threat on the capital, vowing to press on to victory in "an existential war".

Faced with the recent escalation in fighting, the United Nations' Security Council on Friday called for a ceasefire in a rare joint declaration on the issue.

READ MORE: Ethiopia: Tigray rebels kill scores of youths in Kombolcha town

Abiy sent troops into Tigray in November 2020 to topple the TPLF, which he accused of having attacked military bases, promising a swift victory.

But by late June the rebels had retaken most of Tigray and expanded into the neighbouring regions of Afar and Amhara. 

Thousands have been killed and hundreds of thousands forced into famine-like conditions, according to the UN.

Source: TRTWorld and agencies