The Grand Ethiopian Renaissance Dam is set to double the country's electricity generation and become Africa's biggest dam. Egypt fiercely opposes the megaproject, arguing that it will reduce the flow of the Nile river.
Ethiopia said on Sunday it had completed the fourth and final phase of filling a reservoir for its hydroelectric power plant on the Blue Nile river, prompting renewed outcry from Egypt, which has long opposed the megaproject.
The Grand Ethiopian Renaissance Dam (GERD) has been under construction since 2011 at a cost of $4 billion (€3.7 billion). It will be the largest dam in Africa when completed and is expected to produce 6,000 megawatts of electricity -- enough to double Ethiopia's current output.
"Congratulations to all on the fourth filling of the Grand Ethiopian Renaissance Dam," Prime Minister Abiy Ahmed's office wrote on social media on Sunday.
"Our national perseverance against all odds has delivered."
What did Egypt say?
Egypt, which suffers from severe water scarcity and relies on the Nile for 97% of its supply, sees the GERD as an existential threat.
Egypt's Foreign Ministry said Ethiopia's announcement on Sunday was an "illegal" and "unilateral" measure.
The leaders of both countries had held rare talks in July to begin to finalize an agreement for filling the dam and the rules for its operation.
But on Sunday, Egypt's Foreign Ministry said this latest development "places a burden on the course of the resumed negotiations, the next round of which... is hoped will witness a tangible and real breakthrough."
Ethiopia claims the GERD will not reduce the volume of water flowing downstream.