River Nile row: Ethiopia bans flights above Grand Renaissance Dam

While for Ethiopia, the dam, pictured here in 2019, is vital, Egypt sees it is as a threat to its existence

Ethiopia's civil aviation authority has banned all flights over a controversial mega dam being built on a tributary of the River Nile, for security reasons.

Ethiopia sees the $4.8bn (£3.2bn) Grand Ethiopian Renaissance Dam (Gerd) as crucial for its economic growth.

But it has led to bitter disputes with Egypt and Sudan, both of which are downstream and fear the large dam will greatly reduce their access to water.

It comes a week after Ethiopia's air force warned it was ready to defend it.

Speaking on state television last week Maj-Gen Yilma Merdasa said the air force had modernised its fighter jets, and had a "plan A, plan B and so on on how to counter an enemy who knowingly or unknowingly attempts to derail this project".

The head of Ethiopia's civil aviation authority told the BBC on Monday that it was common for the country to ban flights above major projects.

• Africa Live: Updates on this and other stories

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Africa's biggest hydro-electric plant

The dam will produce electricity within the next 12 months, the Reuters news agency quotes President Sahle-Work Zewde as saying. There are already 4.9 billion cubic metres in the reservoir sitting behind the dam - this means that the water level has reached the height of the first two turbines.

Once complete, the Gerd will be the biggest hydro-electric plant in Africa and provide power to up to 65 million Ethiopians.

But Egypt almost totally relies on the River Nile for its water supply and recently warned the dam was "a threat of potentially existential proportions".

Earlier this year, the latest in a long series of talks brokered between the three nations in Washington ended without agreement, although the African Union is still pushing for a deal.

Soon afterwards, Sudan reported a drop in the river's water levels and a reservoir behind Ethiopia's dam started filling up with water, prompting it to warn against "any unilateral actions taken by any party".

Ethiopia initially confirmed satellite images showing the dam water levels rising, saying this was bound to happen with the rainy season, but later backtracked.

In response, the US announced it would cut aid funds to Ethiopia.

"The United States previously and repeatedly expressed its concern that commencing the filling of the Gerd before all necessary dam safety measures were implemented created serious risks," a US state department official told Reuters.