The renewed fighting raged on Friday around the rebel-held town of Marea, 20 km (12 miles) from the Turkish border, the Britain-based Syrian Observatory for Human Rights said. The area falls within a "safe zone" Turkey said last month it would set up in northern Syria to help keep ISIS at bay.

ISIS said late Friday it had waged a fresh assault on Marea, killing "dozens" of Syrian rebels fighting against it. The group last week encircled Marea, taking several villages around the town, in a blow to rebels who are likely partners for Ankara and Washington in any ground campaign. A loss of Marea would make it harder for Turkey and the United States to open a new front against ISIS.

Western-backed rebels have sent in reinforcements from other parts of Aleppo province to try to beat back the militants, according to a rebel fighter. ISIS holds large swathes of territory across Syria and Iraq, and has advanced in other areas of Syria in recent months. It is fighting rival insurgents, the Syrian military and Kurdish regional forces alike in Syria`s four-year-old civil war. Several rebel leaders claimed that ISIS has intensified its attacks on the Turkish border, the strongholds of the opposition groups. The rebels said on twitter that the loss of strategic towns in the north will leave Aleppo trapped between ISIS and the regime and it will lead a new migration wave.

While the Syrian civil war enters its fifth year with no cease-fire or political transition in sight, leaving more than 220,000 people dead and 10 million Syrians displaced, Turkey and the U.S. have reportedly agreed in general terms on a plan to establish a zone to protect the Syrian civilians in the region. Turkish officials said that the safe zone is to provide conditions for refugees to return to Syria. After cleaning the proposed safe zone of ISIS militants and other threats, Turkey`s Disaster and Emergency Management Agency (AFAD) is planning to build refugee camps inside Syria as a first step. According to sources, building roads, permanent accommodations, schools and hospitals are also considered in the long term. Even though the details remain unknown, the plan aims to protect the Syrian civilians, to prevent the refugee crisis from becoming worse than it already is, and to help the neighboring countries, which bear the greatest burden of the crisis and to help stabilize a shattered Syria. Turkey currently hosts more than 1.3 million Syrian refugees, while millions of others have taken shelter in neighboring Iraq, Lebanon and Jordan.

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