AL QASR, Lebanon (AP) -- Masked men in camouflage toting Kalashnikov rifles fan out through a dusty olive grove, part of a group of Hezbollah-backed fighters from Lebanon who are patrolling both sides of a porous border stretch with Syria.
The gunmen on the edge of the border village of al-Qasr say their mission is to protect Shiites on the Syrian side who claim their homes, villages and families have come under attack from Sunni rebels.
Hezbollah chief Sheik Hassan Nasrallah, leader of many of Lebanon's Shiites and a staunch ally of Syrian President Bashar Assad, has said his group is supporting the cadres of fighters who call themselves Popular Committees.
It is confirmation that the powerful Lebanese militant group is playing a growing role in the civil war just across the border.
Syria's regime is dominated by minority Alawites -- an offshoot of Shiite Islam -- while the rebels fighting to overthrow Assad are mostly from the Sunni majority. Assad's major allies, Hezbollah and Iran, are both Shiite.
The sectarian tensions in the civil war have spilled over to neighboring Lebanon, which has a similar ethnic divide and a long, bitter history of civil war and domination by Syria. Deadly gunbattles have broken out in Lebanon in recent months between supporters of both sides of the Syrian war.
But more broadly, Hezbollah's deepening involvement shows how the Syrian civil war is exacerbating tensions between Shiites and Sunnis around the Middle East.
Syrian rebels accuse Hezbollah of fighting alongside Assad's troops and attacking rebels from inside Lebanese territory.
In recent months, fighting has raged in and around several towns and villages inhabited by a community of some 15,000 Lebanese Shiites who have lived for decades on the Syrian side of a frontier that is not clearly demarcated in places and not fully controlled by border authorities. They are mostly Lebanese citizens, though some have dual citizenship or are Syrian.
Before Syria's uprising erupted two years ago, tens of thousands of Lebanese lived in Syria.
The Lebanese Shiite enclave on the Syrian side of the border is near the central city of Homs and across from Hermel, a predominantly Shiite region of northeastern Lebanon.
One commander of the Popular Committees said Shiite villages have been repeatedly attacked and some residents have been kidnapped and killed by rebels. He said that prompted local Shiites to take up arms to defend themselves.
"We are in a state of defense. We don't take sides (between rebels and regime forces). We are here to defend our people in the villages," said the commander, Mahmoud, who gave only his first name out of fear for his own security.
"We don't attack any area. We only defend our villages."
The border region near Homs on the Syria side is strategic because it links Damascus with the coastal enclave that is the heartland of Syria's Alawites and is also home to the country's two main seaports, Latakia and Tartus.
One of the biggest battles in the area was on Thursday when the Syrian army captured Tal al-Nabi Mindo, a village near the Lebanese border, after a day of heavy fighting.
Mahmoud said there were casualties on both sides, adding that the hilltop village overlooks several towns and villages as well as a strategically important road that links Tartus to Homs and the capital of Damascus beyond.
Mahmoud said some rebel commanders were killed in the fighting on Thursday and rebels threatened to bombard Lebanese territory in retaliation.
On Sunday, two rockets fired from Syria exploded in al-Qasr, killing one person, a Lebanese security official said on condition of anonymity because he was not authorized to brief reporters. Two more rockets landed in a nearby village of Hawsh, killing a 13-year-old boy and damaging two homes, the official said. It was unclear who fired the rockets from Syria, the official said.
The Popular Committees were set up last year with the backing of Hezbollah. But even though Hezbollah confirms backing the fighters, it denies it is taking part in the wider civil war.
Syrian rebels offer a different narrative, accusing Hezbollah of propping up the Assad regime.
"Hezbollah is involved in the war that the Syrian regime is launching against the Syrian people," said Loay al-Mikdad, a spokesman for the rebel Free Syrian Army (FSA).
In the past two months, he said Hezbollah has expanded its operations in Syria, mostly in central Homs province near the Lebanese border, as well as in Damascus.
He claimed that Assad is relying on Hezbollah because his grip on the capital is weakening and he fears more military defections.