Addis Ababa (AFP) - The head of a controversial Ethiopian scheme to dam the waters of the Blue Nile was shot in the head on Thursday in a daylight killing in Addis Ababa, police said.

Simegnew Bekele was the project manager and public face of the Grand Ethiopian Renaissance Dam, a massive scheme that has triggered fears among downstream users of the Nile, including Egypt.

Federal police commissioner Zeynu Jemal said Simegnew was shot in the right side of his head, and a gun was later found nearby.

Simegnew had been in his office early on Thursday, he said at a press briefing in the Ethiopian capital.

Images circulating on social media showed a gold Toyota 4X4 with a shattered rear passenger window surrounded by police officers in the downtown Meskel square.

The state-affiliated Fana Broadcasting Corporate earlier reported Simegnew "has been found dead in his car at Meskel Square".

The $4-billion (3.2-billion-euro) dam, being built near the country's western border with Sudan, will be Africa's largest when completed, producing 6,000 megawatts -- the rough equivalent of six large nuclear reactors.

But the scheme faces opposition from Egypt, which is crucially dependent on the Nile and worries that downstream flows could be affected.

In May, Sudan, Egypt and Ethiopia agreed to set up a scientific committee to study the dam's impact.

The Renaissance Dam is one of several "mega-projects" Ethiopia is pursuing that include railways and industrial parks aimed at transforming its economy and pulling the country out of poverty.

Construction started in 2011, and two of its 16 turbines are scheduled to start producing power in 2018, the Ethiopian authorities said earlier this year.

Cairo is primarily concerned at the speed at which the dam's reservoir would be filled.

The Blue and the White Nile converge in Sudan's capital Khartoum and from there run north, crossing Egypt before emptying in the Mediterranean.