Seven fighters from the Lebanese group Hezbollah were killed in a clash with Sunni Islamist militants on the Syria-Lebanon border, according to a monitoring group.
The Syrian Observatory for Human Rights, affiliated to the Syrian opposition, said that the clash in the mountainous border area between Ras al-Maara in Syria and Arsal in northeast Lebanon had also seen 16 rebels killed and 31 Hezbollah fighters wounded.
A Lebanese security official and a Hezbollah source said that at least two fighters and 27 Sunni rebels were killed in the clash. Hezballah did not comment on the alleged deaths of its fighters.
The Observatory said that Hezbollah had captured 14 fighters from different Islamist group including the Nusra Front, the faction who represent al-Qaeda in the civil war.
"It appears Hezbollah launched the attack in a bid to finish off the pockets of rebel resistance," Observatory head Rami Abdel-Rahman said.
Hezbollah is an Iranian-supported Shi'ite Islamist group who have helped Syrian President Bashar al-Assad in the neighbouring four-year Syrian civil war.
The area surrounding Arsal in northeast Lebanon is largely Sunni with locals sympathising with the Sunni uprising against Assad's regime.
Last month, Lebanese Army forces carried out raids in the region to capture militants with ties to "terrorist groups", according to an army statement.