Pass the popcorn.

BEIRUT (WaPo) — Syrian rebels on Tuesday threatened to carry out attacks against Hezbollah inside Lebanon, a dangerous escalation of the conflict that could seriously destabilize Syria’s politically unstable neighbor as well as the region.

Tuesday’s threat to bring the fight to Lebanon, issued by the Free Syrian Army, came after several days of clashes between Syrian rebel fighters and militants from Hezbollah around Qusayr, a Syrian town near the Lebanese border, and a handful of smaller villages in the area, according to the rebels . Hezbollah has not officially responded to the Free Syrian Army statement.

Hezbollah is the most powerful military and political force in Lebanon, and also has an extensive network of social programs. Last fall, Hezbollah leader Hassan Nasrallah admitted that some of the organization’s military personnel are inside Syria, but said they were not involved in combat.

A rebel attack on Hezbollah targets inside Lebanon could have broad regional implications. Hezbollah is closely allied with Iran, who has proven to be one of the strongest backers of Assad. The Syrian rebels, on the other hand, largely have been supported by Turkey, Qatar and Saudi Arabia.

There also is a potentially explosive sectarian dynamic as Hezbollah and Iran are both predominantly Shiite Muslims while the majority of the Syrian opposition, and the bulk of their foreign backers, are Sunni Muslims.

Although Syrian rebels say Hezbollah fighters are involved in clashes in Syrian territory, the Free Syrian Army warning Tuesday specifically addressed the issue of shelling from Hermel, a town in northern Lebanon where Hezbollah has many supporters.The rebels say Hezbollah militants fired rockets from the Hermel area in support of operations carried out by the Syrian military just across the border.

The rebels gave Hezbollah 48 hours to stop the shelling or face retaliation.