Islamic State fighters have taken control of a Kurdish city in northern Syria near the border with Turkey on Thursday after seizing 21 villages, according to The Associated Press.

A surveillance drone was spotted for the first time over nearby Islamic State-controlled territory in Aleppo province, the Syrian Observatory for Human Rights, which tracks Syria's civil war, said, though it was not immediately clear who was operating the drone, the AP reported.

Islamic State fighters seized a group of villages near the city of Ayn al-Arab armed with heavy weaponry including tanks in an offensive which the Observatory said had started on Tuesday night, according to the AP.

President Obama said he would not hesitate to strike the radical Islamist group that has used Syria as a base to advance its plan to reshape the Middle East according to its radical vision of Sunni Islam, the AP reported.

The United States is conducting air strikes against Islamic State in Iraq and last month Obama authorized surveillance flights over Syria, according to the AP.

The Kurds were appealing for military aid from other Kurdish groups in the region including the Kurdistan Workers' Party, the AP reported. Support from Kurds who crossed from Turkey helped to repel an Islamic State attack on Kobani in July.

The Islamic State group and Kurdish militias have been locked in a fierce fight in northern Syria for years, the AP reported.

Footage posted on YouTube on Wednesday by the YPG, the main Kurdish armed group in Syria, appeared to show Kurdish fighters armed with assault rifles and rocket-propelled grenades battling a tank flying the Islamic State's black flag west of Kobani, according to the AP.

The Observatory said there were fears of massacres in the areas seized by Islamic State, according to the AP.