BEIRUT (Reuters) - Islamic State fighters stormed a Syrian town held by Kurdish-led forces near Raqqa city on Monday, part of a wider offensive by the militants two days after their de facto capital was hit by some of the heaviest U.S.-led air strikes in the conflict.
The Kurdish YPG militia said it was fighting to expel Islamic State fighters who had attacked the town of Ain Issa, which was only captured from them two weeks ago with aerial support from the U.S.-led military alliance.
The Syrian Observatory for Human Rights, which reports on the war, said Islamic State forces had taken the town and areas around it some 50 km (30 miles) north of Raqqa city. Air strikes at the weekend destroyed seven bridges over waterways in Raqqa, which is bordered to the south by the Euphrates river, it said.
Monday's attack on Ain Issa was part of a coordinated Islamic State offensive on YPG positions that also targeted the northeastern province of Hasaka, bordering Turkey to the north and Iraq to the south, YPG spokesman Redur Xelil said.
The YPG has been the only notable partner to date on the ground in Syria for the U.S.-led alliance battling to eliminate Islamic State in Syria and northern Iraq, where the group has declared a "caliphate" to rule over all Muslims.
Ain Issa, one of the YPG-held areas targeted on Monday, sits on a major east-west highway that runs all the way from Aleppo in the west to the Iraqi city of Mosul.
YPG-led forces said they had captured Ain Issa on June 23 in part of an offensive that drove deep into Islamic State's stronghold of Raqqa province. They also said they had captured the northern town of Tel Abyad at the Turkish border.
The World Food Programme and local partners delivered 2,000 food rations to Arab, Kurdish and Turkmen families in Tel Abyad last Thursday, enough to last 10,000 people for a month, the U.N. agency said. Islamic State's retreat allowed access to the area for the first time in more than eight months, it said.
In the last two days, Islamic State have attacked YPG-held positions near the northeastern city of Hasaka, which is divided between government and YPG control, and in the Jabal Abdul Aziz mountain range southwest of the city, Nasir Haj Mansour, a Kurdish official in Hasaka province, said.
Hasaka is important in the battle against Islamic State for reasons including its location at the border with territory controlled by the group in Iraq.
The Observatory said Islamic State fighters had seized villages from YPG control in the Jabal Abdul Aziz area. It said the Islamic State offensive stretched all the way from Hasaka province in the north east to the town of Sarin in the north western Aleppo province.
(Additional reporting by Sylvia Westall; Writing by Tom Perry; Editing by Louise Ireland)