Syrian Rebels Strengthen Hold in Country's East Syrian rebels strengthened their hold Thursday on an oil-rich province bordering Iraq, activists said, capturing a key military base that was considered one of the last bastions for President Bashar Assad's loyalists in the strategic region. The reported fall of the Mayadeen base, along with its stockpiles of artillery, caps a series of advances in Deir el-Zour including last week's seizure of a military airport. The province borders on western Iraq. Syria's rebels enjoy strong support with the Sunni tribes of Iraq's west, and many Iraqis with combat experience from their own war are believed to have crossed to fight in their neighbor. Rebel fighters also say that weapons seized when bases fall have been essential to their transformation from ragtag brigades into forces capable of challenging Assad's professional army. Activist groups and a local fighter told The Associated Press the Mayadeen base was taken in the morning hours, after a three-week siege. Violence also was reported in opposition strongholds around the capital Damascus and in the northern city of Aleppo, where government aircraft damaged one of the rebels' key field hospitals. Rebels who have battled government forces for months to control Aleppo, Syria's economic hub, scored a major victory several days ago when they overran the nearby base of the regime's 46th Regiment. The unit was a pillar of the government's Aleppo garrison and its fall cuts a major supply line. However, the regime has used its air power to dent rebel gains. Government aircraft late Wednesday flattened a building next to Dar al-Shifa hospital, killing 15 people and badly damaging one of the last remaining sources of medical help for civilians in the city, activists said. Once a private clinic run by a businessman said to be close to Assad, Dar al-Shifa became a field hospital run by volunteer doctors, nurses and aides united by their opposition to the regime. They gave medical care to both civilians and rebels. The facility has taken at least six direct shell hits in recent months, mostly affecting the upper floors. The seven-story hospital is only 400 to 500 meters (yards) from the front line in a neighborhood that is heavily shelled every day. Rami Abdul-Rahman, chief of the British-based Syrian Observatory for Human Rights, said at least 11 fighters were killed in the raid, in addition to a doctor, a young girl and two children who were on the street. Videos posted online by activists showed the flattened building. Residents and rebels along with a doctor in green scrubs are seen picking through the rubble and overturned gurneys outside the hospital entrance. In one video, a man calls out to survivors under the rubble, while one of the survivors is heard crying for help from beneath a huge slab of concrete.