A resident carries an injured civil defence member in the neighborhood of Aleppo on July 27. (Reuters)

More than 2,000 Syrians — almost half of them pro-government forces — have been killed in just under two weeks of fighting in Syria, marking one of the worst death tolls in the country’s three-year civil war, opposition activists said Monday.

The reports reflect a recent surge in deadly attacks by the al-Qaeda-breakaway Islamic State group targeting President Bashar al-Assad’s forces, signaling shifting priorities as Sunni militants seek to consolidate their hold on territory and resources in northern Syria.

Forces loyal to Assad had gained momentum in the fighting with rebels seeking to topple him from power, with infighting between the Islamic extremists and more moderate anti-Assad groups also hurting the rebel cause.

But a string of recent setbacks for Assad’s forces at the hands of the Islamic State threatens to overturn government successes, pitting the army against a formidable force that now controls large chunks of territory in the country’s north and in neighboring Iraq.

“Now that they’ve mopped up rebel resistance to them in the east, the Islamic State can turn to the regime,” said Aymenn al-Tamimi, an expert on militant factions in Syria and Iraq. “The assault against the regime was inevitable.”

The recent attacks came after Assad was reelected last month to a third, seven-year term in a vote that was confined to government-controlled areas and dismissed by the opposition and its Western allies. In his inauguration speech July 16, he declared victory and praised his supporters for “defeating the dirty war.”

Since then, Islamic State fighters have attacked army positions in three provinces in northern and central Syria. In the past week alone, the militants captured a government-controlled gas field and two major army bases.

More than 300 soldiers, guards and workers at the Shaer gas field were reported killed in a three-day militant offensive. The army recaptured Shaer over the weekend.

Militants last week also overran the sprawling Division 17 military base in northern Raqqah province, killing at least 85 soldiers. Amateur videos posted online by activists showed more than a dozen beheaded bodies in a busy square said to be in Raqqah. Some of the heads were placed on a nearby fence, where at least two headless bodies were crucified.

On Sunday, the militants seized the army’s Regiment 121 at Maylabieh in the northern province of Hasakah after a three-day battle.

Beyond Syria, the Islamic State fighters have seized large swaths of land in northern and western Iraq and have declared a self-styled caliphate across territory straddling the Iraq-Syria border.

The Britain-based Syrian Observatory for Human Rights said more than 2,000 people have been killed since Assad’s inauguration, nearly half of them soldiers and government-allied militiamen.

It did not provide a breakdown for the rest of the casualties, which would include civilians and opposition fighters.

The Syrian government has not reported on the heavy losses.

— Associated Press