Yemeni warplanes struck tribesmen Wednesday suspected of sabotaging power lines a day earlier, leaving the country without electricity and prompting angry protests in the capital.
Officials have accused the tribesmen of blocking the road linking Sanaa to the eastern province of Marib, making it impossible to carry out repairs.
Wednesday's air strikes targeted a gathering of tribesmen near Marib, a tribal source said, without immediately being able to provide a casualty toll.
Another tribal source said the saboteurs were protesting against Marib's governor, whom they accuse of seizing government subsidies destined for the tribes.
Deeply-tribal Yemen has suffered a total blackout since Tuesday, with the entire national power and energy grid down, including Marib's gas plant, according to the electricity and energy ministry.
Attacks on power lines in Yemen are common and often launched by tribesmen as a lever to press for the release of jailed relatives or to support other demands.
The absence of reliable electricity supplies further complicates the lives of Yemenis, who already suffer water and food shortages.
Enraged by the power cuts added to weeks of severe fuel shortages, with motorists having to queue for hours at petrol station, thousands took to the streets in Sanaa Wednesday.
Protesters marched towards Sittin Street, where President Abdrabuh Mansur Hadi lives, demanding the government's ouster.
"The government of (Prime Minister Mohamed) Basindawa does not care about citizens," said taxi driver Taha al-Amrani.
"Poor people like myself wait two days in a queue for 40 litres of gasoline. This is not a life," he said angrily. "My children are going to starve."
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Police fired warning shots as protesters, some armed, set tyres ablaze.
Interior Minister Abdo al-Tarib went into the streets to calm the situation, telling protesters "we are all going through difficulties."
- Pipeline attacks cost '$300 mn'-
An 11-month-long Arab Spring-inspired uprising against former president Ali Abdullah Saleh led to his ouster in 2012, and a consensus government of his opponents and loyalists was formed following his resignation.
"We took to the streets three years ago demanding changes and today we are asking President Hadi to listen to our calls and change the government," said Maziar, a member of the so-called "Youths of the Revolution" who led the protests against the former regime.
"Our revolution will continue until our goals are achieved," he said.
Describing the energy crisis as "complex," Deputy Oil Minister Shaw qi al-Akhlame said "saboteurs, the government and bandits" are all responsible.
He told AFP the electricity ministry has debts it has not been paying to the oil ministry and "Yemen has lost $300 million in one year" due to the repeated attacks on oil pipelines in Marib.
Meanwhile, "gunmen" have seized "200 gas and 80 fuel trucks" on the road between Marib and Sanaa, he said.
The fuel shortage has also affected students.
"We are unable to study due to the power outage or move around due to the lack of taxis," lamented one student, who said he was forced to make a long journey on foot to reach his examination centre.