NAIROBI, KENYA -- Ethiopia's government on Wednesday said its military could re-enter the capital of its embattled Tigray region within weeks, calling into question the unilateral ceasefire it declared in Tigray just days ago.

Ethiopia also asserted that soldiers from neighbouring Eritrea, who had been collaborating with Ethiopian forces, had withdrawn from Tigray. That could not immediately be confirmed and Eritrean officials did not respond to questions, but the withdrawal would be another major development in the nearly eight-month war.

Redwan Hussein, spokesman for the Tigray emergency task force, spoke to reporters in Ethiopia's first public remarks since its soldiers retreated from the Tigray capital and other parts of the region on Monday in a dramatic turn in the fighting.

The Tigray forces that have retaken key areas after some of the war's fiercest fighting have rejected the ceasefire, telling The Associated Press it was a "sick joke' and vowing to chase out Ethiopian and Eritrean forces.

There will be no negotiations with Ethiopia until communications, transport and other services that have been cut or destroyed for much of the war are restored, the Tigray forces' spokesman, Getachew Reda, told the AP on Wednesday.

"We have to make sure that every inch of our territory is returned to us, the rightful owners," Getachew said, adding that Ethiopian forces are still fighting to regain territory and Eritrean forces still control a "significant part" of the region.

That contrasted with Redwan's comment that "the Eritrean army has withdrawn" from Tigray. He didn't respond to questions for more details. The United States on Tuesday said it had not yet seen a statement from Eritrea saying it was committed to the ceasefire.

The situation in Tigray remained "extremely fluid," the United Nations said, adding that Tigray forces now control the regional capital, Mekele, as well as Shire and the towns of Axum, Adwa and Adigrat.

One aid worker told the AP their organization's internal assessments showed that Eritrean forces had only pulled back to border areas. The aid worker, speaking on condition of anonymity for fear of retaliation, added that "several thousand" Tigray fighters passed through Shire on Wednesday morning, saying they were going to Hitsats to the west to fight.

The long-time president of Eritrea, Isaias Afwerki, has long been an enemy of Tigray's leaders, who for years dominated key positions in Ethiopia's government and military before being sidelined by Prime Minister Abiy Ahmed. Witnesses have accused the Eritrean soldiers of some of the worst atrocities in the conflict.

"We will do anything in our power to make sure that Isaias will never be a threat again," the Tigray forces' spokesman said. Eritrea shares a long border with the Tigray region along which it and Ethiopia fought a war in 1998-2000.

With the current war likely to continue, the fate of more than 1 million Tigrayans in hard-to-reach areas is in question as Ethiopia and authorities on the ground are accused of blocking access for the delivery of aid. Phone and internet services remain cut.

Ethiopia has said it declared the ceasefire in part on humanitarian grounds, but said it would end once the crucial farming season in Tigray is over, which means September.

Seeking to explain this week's dramatic retreat, Ethiopian Lt. Gen. Bacha Debele on Wednesday said the military had to move forces from Tigray to face "bigger threats" and referred to the border, but denied the possibility of a conflict with neighbouring Sudan over disputed lands.

Some observers expressed concern that the warring sides wouldn't use this new period to pursue a peaceful resolution in Tigray.

"The fear is that the Tigrayan forces are not going to be interested in negotiating, even though they are now in a position of strength," said Ahmed Soliman, a researcher with Chatham House. "The (Ethiopian) government might also use this period (of rainy season) to regroup and reinforce in anticipation of future conflict. That would be a missed opportunity."

Speaking to reporters at UN headquarters, Russia's UN Ambassador Vassily Nebenzia said the Ethiopian government's announcement of a unilateral ceasefire "gives us a light glimmer of hope, because we always said there is no solution to any crisis which ... is waged by military means."

"There is no solution to this crisis by military means, only a political solution will work," Nebenzia said. "How that will translate in what is happening in Ethiopia -- is it a temporary lull or is it a road which will pave the way to the political settlement? That is a question to be addressed."

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Edith M. Lederer at the United Nations contributed.