At least 34 Islamic State (IS) militants were killed on Thursday in clashes with Kurdish forces and US-led international coalition airstrikes in northeastern Syria, the Syrian Observatory for Human Rights (SOHR) reported.The NGO said 32 of the jihadis were killed in and around Ain Issa, 50 km north of al-Raqqa, the main IS stronghold in Syria.Fighting returned to Ain Issa on Thursday when IS regrouped to take back the city after being expelled by the Syrian Kurdish People's Protection Units (YPG) on Wednesday.Two other IS fighters were killed in the southwest of al-Hasakah province, in the northeast of the war-torn country.On Monday, IS launched an offensive against Kurdish positions in the area of Jabal Abdulaziz, also in the southwest of al-Hasakah, in Serrin, south of the Syrian Kurdish enclave Kobani, near the border with Turkey, and in Ain Issa.Meanwhile, in the central province of Homs, the Syrian army has been advancing on the jihadis, fighting just five km west of the historical city of Palmyra, taken by IS on May 20.