Islamic State kills dozens of opposition fighters in Syria

At least 50 people, including women and children, were killed by militants led by the self-proclaimed Islamic State (IS) as they clashed with opposition forces near the northeastern town of Akhtarin in Syria's Aleppo province late Wednesday.

Fierce clashes erupted after IS militants seized control of the opposition-held town and nearby villages earlier in the day, Yaser Ahmed, media officer for the pro-opposition Local Coordination Committees of Syria, told the Anadolu Agency.

Amid ongoing clashes between militants and armed opposition forces, many locals in the region have reportedly begun fleeing to Azaz district near the country's border with Turkey.

Analysts have said the capture of Akhtarin on Wednesday is significant because it gives IS control of key supply routes between Syria and Iraq as it seeks to expand and hold territory in its self-declared caliphate.

Since joining the conflict in Syria in spring 2013, IS has seized much of Raqqa and Deir Ezzor provinces on the border with Iraq, including the area's oil fields, and the group's nerve centre is now in Raqqa, said Fawaz Gerges, professor of international relations at the London School of Economics.

Only Raqqa's military airport, which a local activitist said IS militants were attacking with heavy weapons on Wednesday, remains in Syrian government control, Gerges said.

The US, which began airstrikes against Islamic State militants around Iraq's Sinjar mountain range, will be forced to turn their attention to fighting IS in Syria, where they are now headquartered, if they want to halt the group's expansion, he added.

As Islamic State militants continued their campaign towards the northern Syrian city of Aleppo, Syrian troops continued to shell the city with barrel bombs, killing 17 people on Wednesday, according to the Syrian Revolution General Commission.

Months of barrel bombing are slowly reducing Aleppo to rubble, while lack of maintenance for vehicles and the terrible road conditions in the city have meant that many are dying simply from being unable to reach the few remaining medical centres.

Syria has been gripped by civil war since March 2011. Last month, the Syrian Network for Human Rights reported that more than 133,000 people had been killed in the Syrian civil war.