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The Syrian army and members of Lebanon's militant Hezbollah group launched a major ground offensive on Friday aimed at ending the yearslong presence of hundreds of militants in a border area between the two countries.

The offensive was widely expected after negotiations with militants to leave the area failed over the past days. The battle will be fought by Syrian troops and Hezbollah gunmen on the Syrian side of the border while the Lebanese army will likely fight against the militants on the Lebanese side.

On Tuesday, Lebanese Prime Minister Saad Hariri said the country's military is preparing a military operation to secure a lawless section of the border with Syria while Hezbollah leader Sheikh Hassan Nasrallah hinted in a speech last week that a joint operation was in the works with the Lebanese and Syrian militaries to expel insurgents from the border area.

Government-controlled Syrian Central Military Media reported that military operations began early Friday from two fronts on the outskirts of the Lebanese town of Arsal and the Syrian village of Fleeta. Arsal is about 80 kilometers (50 miles) south of the Syrian city of Homs.

It said Syrian troops and Hezbollah fighters captured some areas from the militants and killed and wounded a number of extremists.

The opposition's Britain-based Syrian Observatory for Human Rights said Syrian warplanes struck the area. It added that Syrian troops and Hezbollah fighters captured some areas from insurgents.

The rugged mountainous region is a stronghold of Syria's al-Qaida's branch, known as Jabhat Fatah al-Sham or Fatah al-Sham Front, as well as the Islamic State group and the Levant People's Brigades. Friday's fighting concentrated in areas controlled by JFS.

Video released by SCMM shows Hezbollah's artillery pounding militant positions while drone footage showed smoke billowing from areas controlled by the militants.

Lebanon's state-run National News Agency said the Lebanese army shelled an area on the border to prevent a group of militants from entering the Arsal area. It added that the Lebanese army has asked air organizations to accompany Syrian refugees who want to flee the fighting to safer areas.

There will be concerns about civilian casualties if the militants infiltrate Arsal, which is home to tens of thousands of Syrian refugees who fled civil war in their country.

The militant-held areas are surrounded from all sides leaving them with no place to withdraw to.

Hezbollah says the border area has been used in the past to launch attacks deep inside Lebanon, including a wave of bombings since 2013 that have killed scores of people.

In 2014, militants briefly stormed Arsal and captured more than two dozen Lebanese soldiers and policemen. Al-Qaida exchanged the troops it was holding while nine soldiers taken by IS fighters are still missing.

The attack in the Lebanon-Syria border area came as fighting between two of Syria's strongest military groups spread in the rebel-held northwestern province of Idlib with al-Qaida-linked fighters trying to capture a main border crossing point with Turkey.

Friday's fighting between the ultraconservative Ahrar al-Sham and al-Qaida-linked Hay'at Tahrir al Sham — Arabic for Levant Liberation Committee — that is also known as HTS, focused on the Bab al-Hawa crossing.

HTS, a coalition of several insurgent groups, suffered a blow a day earlier after the powerful Nour el-Din el-Zinki faction withdrew in protest against the fighting with Ahrar al-Sham.

The Observatory said that HTS was not able to capture the border crossing. It added that a convoy of fighters from Nour el-Din el-Zinki and Failq al-Sham headed to the fight with the objective of dividing the two groups.

The group said three days of fighting between the two rival groups left 85 people dead, including 68 fighters from both sides.

The HTC-linked Ibaa news agency said al-Qaida-linked fighters captured a hill known as 106 that overlooks the Bab al-Hawa border crossing, one of the main sources of income for Ahrar al-Sham.

Ahrar al-Sham's top commander, Ali al-Omar, said in a video released Friday that attacks by HTS are "an aggression against the Syrian revolution," warning that the hand that will try to harm the anti-government revolution "will be amputated."