Islamist rebels claim they have seized Syria's largest oil field, potentially cutting off President Bashar al Assad's supply of almost all local crude reserves.
If confirmed, the loss of the al-Omar oil field in the eastern Deir al-Zor province could leave Assad's military forces relying almost entirely on imported oil in their campaign to crush the rebel uprising.
It came as the Syrian Observatory for Human Rights reported at least 29 deaths following regime air strikes in northern Aleppo, including 14 people who were killed in the city's eastern district of Tariq al-Bab.
Video posted online by Syrian activists showed dozens of people picking through the rubble of collapsed buildings and throwing buckets of water on a destroyed car still in flames.
It was also claimed that another 15 people, including a woman and a child, were killed in air strikes on the nearby town of al-Bab and the Tadef area.
Rami Abdelrahman, head of the Syrian Observatory for Human Rights, claimed the capture of al-Omar meant "nearly all" of Syria's oil reserves are now in the hands of Islamist units, including the al-Nusra Front.
"The regime's neck is now in Nusra's hands," he said.
Amateur video posted online appeared to show insurgents spreading out across al-Omar.
One rebel, who spoke to the camera in Arabic, said: "The field is going to be managed perfectly. We are going to keep it safe. We are going to run the oil field in a good way and better than before."
The Syrian army lost control of al-Omar in November 2012 but later recaptured it.
Until the insurgents' alleged seizure of the facility, a pipeline transporting crude oil to central Syria for refinement had still been working, despite the civil war.
International sanctions against Syria have sharply reduced its oil exports and the conflict has made production for domestic consumption increasingly difficult.
Most oil reserves are now in the hands of rebels, local tribes or Kurdish militias, some of whom may be willing to sell oil to Assad, who may be getting fuel from Iran, his main regional ally.
More than 120,000 people have been killed since the conflict in Syria began in March 2011.