Egypt has voiced anger after Ethiopia announced it had filled the reservoir at a highly controversial hydroelectric dam on the Blue Nile river.
Ethiopia has been in dispute with Egypt and Sudan over the megaproject since its launch in 2011. Egypt relies on the Nile for nearly all its water needs.
Egypt's foreign ministry said Ethiopia was disregarding the interests of the downstream countries.
Ethiopia says the $4.2bn (£3.4bn) dam will not cut their share of Nile water.
"It is with great pleasure that I announce the successful completion of the fourth and final filling of the Renaissance Dam," Ethiopian Prime Minister Abiy Ahmed said on X, formerly Twitter.
He admitted the project had faced "internal and external obstacles" but "we endured all that". The dam began generating electricity in February 2022.
Ethiopia believes the Grand Ethiopian Renaissance Dam (Gerd) will double the country's electricity output, providing a vital development boost, as currently half the 127-million population lacks electricity.
The plan is to generate more than 6,000 MW at the dam, which is about 30km (19 miles) from Ethiopia's border with Sudan.