BEIRUT - Syrian government troops on Thursday flushed out rebels who had stormed a prison compound in the northern city of Aleppo in a bid to free hundreds of political prisoners.

The forced retreat was the latest setback for fighters seeking to topple President Bashar al-Assad, whose forces have been gaining ground in the country's civil war.

In Washington, President Obama and the Turkish prime minister projected a united front on Syria, despite sharp differences about how much the U.S. should intervene.

"There's no magic formula for dealing with an extraordinarily violent and difficult situation like Syria," Obama said at a joint news conference with Prime Minister Recep Tayyip Erdogan in which he pledged that the United States and Turkey would ramp up pressure to oust Assad from power.

Forces loyal to Assad have recently made advances in strategically important locations across the country, including in areas around the capital, Damascus, and in the country's south, near the border with Jordan.

The troops have been bolstered by the world's reluctance to take forceful action to intervene in the fighting.

Assad has also benefited from the rapid rise of al-Qaeda-linked extremists among the rebels, which has raised alarm in the West. Militant groups, including Jabhat al-Nusra, which is designated a terrorist group by the United States, have emerged as one of the most potent fighting forces in the uprising against Assad.

A video emerged Thursday showing a Nusra Front commander killing 11 regime soldiers execution-style for alleged crimes they committed against the Syrian people.

Rami Abdul-Rahman, director of the Syrian Observatory for Human Rights, whose group distributed the video, confirmed the killings took place late last year in eastern Deir el-Zour province and identified the Nusra commander as a Saudi known by the name Qusoura al-Jazrawi. He said the man was killed in March in battles with local gunmen.