At least 500 rebels on Wednesday crossed the Turkish border, a monitor said, and headed for the Syrian town of Azaz in northern Aleppo province where opposition forces have suffered setbacks at the hands of Kurdish fighters.



“At least 500 rebels have crossed the Bab al-Salam border crossing on their way to the town of Azaz, from which they want to help the insurgents in the face of gains made by Kurdish forces in the north of the province,” the head of the Syrian Observatory for Human Rights, Rami Abdel, told Agence France-Presse.

They included rebels as well as Islamist fighters, all of them armed, he said.

Almost 350 rebels were also reported to have passed through the Atme border crossing on 14 February armed with heavy and light weapons.

Opposition forces have lost ground to government troops in northern Aleppo province since they began a major offensive in the former rebel bastion backed by Russian airstrikes.

Pressing their advantage, Kurdish forces have been taking ground in the fragmented region, most notably the city of Tal Rifaat, as they seek to carve out their own autonomous state.

The rebels now hold only the town of Azaz, not far from the Turkish border, and to the south Marea, encircled by Kurdish forces to the west and Islamic State fighters to the east.

Alarmed by the Kurds’ gains close to its border, Turkey, which supports the groups opposing Syrian President Bashar al-Assad, has continued shelling their positions.

The UN secretary general, Ban Ki-moon, warned on Wednesday that escalating military activity in Syria and threats of further use of force risked derailing efforts to reconvene peace talks and find a political solution to the five-year-old war.

Ban was delivering his first report to the security council on implementation of a council resolution adopted in December that endorsed a peace process for Syria, including a ceasefire and talks between the Damascus government and opposition.

The resolution was supported by 17 key countries supporting opposing sides of the Syrian conflict who agreed on 12 February to a “cessation of hostilities” in Syria within a week. But that appears less and less likely as government forces aided by the Russian bombing campaign try to encircle the rebels in Aleppo and cut off their supply route to Turkey.

Ban reiterated his call for the security council to refer the Syrian crisis to the international criminal court for investigation of possible war crimes. An attempt in May 2014 was supported by 13 council members but vetoed by Russia, Syria’s closest council ally, and China.