A Hezbollah commander was killed outside of his house in Beirut on 4 December.
In a statement, the Lebanese militant group blamed Israel for the assassination of Hassan Lakkis, though Israel has denied the accusations. On Twitter the little-known group Free Sunni Brigades of Baalbek claimed responsibility for the killing.
The assassination is the latest incident attributed to Syrias civil war in which Hezbollah is militarily supporting regime forces.
That has led to much of the recent violence in Lebanon being directed at Hezbollah and its ally Iran, including the recent bombing of the Iranian embassy in Beirut that killed at least 23 people and injured nearly 150.
But Syrias war spillover has also caused an increase in sectarian violence. During the weekend of 1 December, gun battles escalated in Tripoli, located in the north of the country near the Syrian border, killing at least 12 and injuring more than 100 people. The conflicts prompted Lebanons government to put its army in control of the countrys second-largest city for the next six months.
It was not the first time violence occurred in Tripoli. Over the past two years, sporadic gun battles erupted in the city and in August, two bombs near mosques killed over 40 people, wounding over 500.
Tensions are also reaching new heights between Lebanese citizens and Syrian fugitives. On 2 December, residents of a village in the east of Lebanon burnt down a campsite of Syrian refugees, forcing hundreds from their homes.
About 1 million Syrians have fled to Lebanon, home to 4 million people, over the past two years. State officials and aid workers have expressed concern over the situation, as the refugees do not always get along with Lebanese citizens and the government feels burdened by the high costs associated with hosting them.