By Suleiman Al-Khalidi
AMMAN (Reuters) - Syrian rebel forces closed in on a town near the Turkish border held by Islamic State militants on Tuesday after seizing numerous villages from the group in the area, rebels and the Syrian Observatory for Human Rights said.
The rebels involved in the offensive include factions fighting under the banner of the Free Syrian Army that have been supplied with weapons via Turkey. They are advancing towards the IS-held town of al-Rai.
A sustained rebel advance near the Turkish border would erode Islamic State's last foothold in an area identified by the United States as a priority in the fight against IS.
Rebels who have previously struggled to make sustained gains against IS in the area have mobilised several thousand fighters for the attack, rebel sources said. An alliance of rebel groups formed for the offensive includes the Turkish-backed Sultan Murad and Failaq al Sham groups.
"The battles are continuing ... we have been able to liberate several villages very quickly from the Daesh (IS) gangs and God willing will cleanse northern Aleppo," Abu Yasser, a commander with Failaq al Sham group, speaking to Reuters.
The Observatory said the rebel groups had seized at least 16 villages in an area held by IS for nearly two years.
Islamic State's foothold at the Turkish border was significantly loosened last year by U.S.-allied Kurdish fighters of the YPG, which gained territory from the group further east.
The YPG and rebels are however locked in their own conflict, notably near the city of Aleppo. Turkey, a major sponsor of groups fighting to topple President Bashar al-Assad, has been alarmed by YPG gains near the frontier with Syria.
Clashes that broke out at dawn on Tuesday when Islamist rebels launched attacks on the Kurdish-held Sheikh Maqsoud neighbourhood in northern Aleppo city still raged later in the day, the Observatory said.
Dozens of mortars fired by the rebels killed 10 people and injured some 30 more. Four YPG fighters and a number of rebels were killed in the clashes, according to the Observatory.
During the fighting, rockets were launched after Kurdish YPG units were able to make gains from Sheikh Maqsoud and disrupt the Castello highway, the main route for civilians and rebels into rebel-held parts of the city.
(Reporting by Suleiman Al-Khalidi, additional reporting by John Davison in Beirut; Editing by Tom Perry/Mark Heinrich)