And for the first time, Syrian rebels have threatened to take the fight to Hezbollah inside Lebanese territory, a potentially dangerous expansion of the conflict.
Hezbollah is the most powerful political and military force in Lebanon. It is also a group supported primarily by Shiite Muslims, many of whom back the government of Syrian President Bashar al-Assad. The opposition in Syria is made up of mostly Sunni Muslims and has broad support among Sunnis in Lebanon.
Sunni militant groups from Lebanon have also been sending fighters into Syria and giving weapons and logistical support to the opposition, according to Lebanese security officials. Now, tensions are peaking as Shiites and Sunnis from Lebanon are fighting one another inside Syria, increasing the potential for conflict back home.
The fighting on the border could easily spread to Tripoli, Sidon or even Beirut, cities where heavy clashes in the past two years between Shiites and Sunnis linked to the Syrian conflict have left dozens dead.
The conflict also has regional implications. Hezbollah has linked with Iran to form an axis of Shiite support for Assad, whose Alawite sect is an offshoot of Shiism, while Turkey, Qatar and Saudi Arabia have formed a grouping of predominantly Sunni powers that support the opposition.
In a report to the U.N. Security Council last week, U.N. Secretary General Ban Ki-moon expressed “grave concern” about the “further deaths of Hezbollah members fighting inside Syria” as well as reports of Sunni Lebanese fighters being killed in Syria.
“The dangers for Lebanon of such involvement and indeed of continued cross-border arms smuggling are obvious,” he said. “I call upon all Lebanese political leaders to act to ensure that Lebanon remains neutral in respect of external conflicts.”
In a speech Wednesday, Hezbollah leader Hassan Nasrallah acknowledged that there are Hezbollah militants fighting in the villages near the border and said the residents there have a right to defend themselves. He also issued a stern warning, saying, “No one should make any miscalculations with us.”
Observers say that one misstep from Shiite or Sunni militants on Lebanese soil could cause the situation to deteriorate quickly.
“They are involved in the war on the other side, but they are trying not to bring it to Lebanon. The problem is, this thing can collapse at any moment,” said Timur Goksel, a former senior adviser to the U.N. monitoring team in Lebanon who is a political science lecturer at the American University of Beirut. “We may have a very serious outbreak of violence in Lebanon. So that’s what is scary.”