BEIRUT (AP) — Tribesmen have risen up against the extremist Islamic State group in eastern Syria, forcing it to withdraw from three villages after heavy clashes that left more than a dozen people dead, activists said Saturday.

It was the first sign of local resistance to the extremist group since its fighters captured large parts of the oil-rich eastern province of Deir el-Zour in recent weeks.

The Syrian Observatory for Human Rights and Turkey-based activist Mustafa Osso said the group was forced to bring in reinforcements from neighboring Iraq after members of the Shueitat tribe drove jihadi fighters out of the villages of Kishkiyeh, Abu Hamam and Granij.

The Observatory, a Britain-based group relying on activists inside Syria, said tribesmen torched the local headquarters of the Islamic State in the nearby town of Ashara and that residents held a demonstration against the group.

Osso and the Observatory said fighting first broke out Wednesday after jihadis detained three tribesmen, allegedly breaking an agreement between the two sides reached after Islamic State fighters captured the villages.

The al-Qaeda breakaway Islamic State took over large swaths of western and northern Iraq in June. The group has declared a self-styled caliphate in territory it controls along the Iraqi-Syrian border, imposing a harsh interpretation of Islamic law.

“There has been wide resentment recently because of Islamic State’s acts,” said Osso, who is in contact with activists in different parts of Syria. He said one of the group’s top commanders, an ethnic Chechen known as Omar al-Shishani, is believed to be leading the jihadis in the area.

Osso added: “This is a very important area for Islamic State because it is rich with oil and borders Iraq.”

The Observatory said tribesmen captured the nearby Tanak oil field on Friday. It added that the Islamic State has sent a large number of fighters from the Iraqi border town of Qaim to reinforce the group’s positions.

The Observatory said four days of fighting left nine jihadis, three tribesmen and five civilians dead.

In a separate incident, the Observatory said Syrian troops and members of Lebanon’s Hezbollah group ambushed a large number of opposition fighters in the Qalamoun region near the border with Lebanon on Saturday, killing at least 50 of them. It said seven troops and Hezbollah fighters were killed in the fighting.

Syrian state TV reported clashes in the Qalamoun region in which “tens of terrorists” were killed. Syrian media refers to all opposition fighters as terrorists.

Government troops backed by Hezbollah have seized nearly all the strategic Qalamoun region since launching an offensive there last November, severing rebel supply lines from neighboring Lebanon.

The Syrian uprising began in the form of peaceful protests against President Bashar Assad in March 2011, but escalated into an insurgency when government forces violently cracked down on dissent.

The country is now in the grip of a complex civil war pitting several rebel and Islamic extremist groups against the government and each other. Over 170,000 people have been killed in Syria in more than three years of fighting, activists say.

Copyright 2014 The Associated Press.