Two senior commanders from a the Lebanese group Jamaa Islamiya were killed by an Israeli strike in eastern Lebanon on Friday, the Sunni Islamist group confirmed on Friday.
The group said in a statement that Mosab Saeed Khalaf and Bilal Mohammed Khalaf "died while carrying out their tasks... in a Zionist strike in the Bekaa" valley.
It was not immediately clear if the two men were relatives.
A Lebanese security source earlier reported that an Israeli drone attack killed one member of the Jamaa Islamiya who was in a vehicle on the road to Meidun in the Bekaa Valley.
Israel's military confirmed the report, naming the man as Mosab Khalaf and describing him as a "senior terrorist in the Jamaa Islamiya" group.
An Israeli "aircraft struck and eliminated Mosab Khalaf in the area of Meidun in Lebanon", it said, accusing Jamaa Islamiya of planning attacks on the Shebaa Farms - an area of Lebanon occupied by Israel.
It also claimed Khalaf "cooperated with the branch of the Hamas terrorist organisation in Lebanon, coordinating and carrying out terror attacks against Israel".
Friday's attack follows an uptick in clashes between Israel and Lebanon's Hezbollah group, with near-daily cross-border incidents.
Israeli strikes have killed at least 383 Lebanese, mostly Hezbollah fighters, and 70 civilians.
Israeli strikes have also targeted and killed journalists reporting in the border area between the two counties, drawing international condemnation.
Additionally, tens of thousands of Lebanese citizens have been displaced as a result on the cross-border fighting.
Hezbollah said Friday it had launched "dozens of Katyusha rockets" at two Israeli military posts in northern Israel "in retaliation for the enemy's attacks, specially the cowardly assassination" operation, without elaborating.
Lebanon's Jamaa Islamiya is a Hamas ally and has claimed attacks on Israel from southern Lebanon.
In March, a Jamaa Islamiya official reportedly survived an Israeli drone strike in eastern Lebanon and the group said three of its fighters were killed in Lebanon's south.
The tensions between Hezbollah and Israel, who last went to war in 2006, has fuelled fears of all-out conflict in the country amid Israel's ongoing military onslaught in Gaza, which has killed 34,388 Palestinians - mostly women and children.