The overt Hezbollah involvement several funerals for group members were held Monday in Lebanon edges the war further into a regional sectarian conflict pitting the Middle East's Iranian-backed Shiite axis against Sunnis.
It also raised tensions considerably in Lebanon, where Hezbollah has come under harsh criticism for its involvement in the civil war next door.
A staunch ally of Syrian President Bashar Assad, Hezbollah is heavily invested in the survival of the Damascus regime and is known to have sent fighters to aid government forces. The Iranian-backed group's growing role in the conflict also points to the deeply sectarian nature of the war in Syria, in which a rebellion driven by the country's Sunni majority seeks to overthrow a regime dominated by Assad's Alawite sect, an offshoot of Shiite Islam.
Clashes continued for the second day in the northern city of Tripoli, Lebanon, where Sunnis and Alawites battled in a direct spillover from the fighting in Qusair.
The Britain-based Syrian Observatory for Human Rights, which tracks Syria's civil war, said that more than 70 Hezbollah fighters have also been wounded in the fighting around Qusair.
The White House said President Barack Obama telephoned Lebanon's president and expressed concern about Hezbollah's "active and growing role in Syria, fighting on behalf of the Assad regime, which is counter to the Lebanese government's policies."
More than 70,000 people have been killed and several million displaced since the uprising against Assad erupted in March 2011 and escalated into a civil war. The Syrian government and Hezbollah deny there is an uprising in Syria, portraying the war as a foreign-backed conspiracy driven by Israel, the U.S. and its gulf Arab allies.
In addition to the Hezbollah involvement, Iraqi Shiite fighters have for months trickled into Syria. Their relatives say they are drawn by a sense of religious duty to protect Shiite Muslim shrines in Syria.
Hezbollah leader Sheik Hassan Nasrallah said in a recent speech that his fighters had a duty to protect the shrines. He also claims that supporters of the group were fighting in Shiite villages near the Lebanon border against the rebels, saying it was in self-defense.
The Observatory, which relies on a network of activists inside Syria, cited unidentified "sources close to the militant group" for its Hezbollah death toll Monday. It said at least 50 Syrian rebels also were killed in the battle for Qusair on Sunday.
Qusair has been the target of a Syrian government offensive in recent weeks, and the surrounding countryside has been engulfed in fighting as regime troops backed by Hezbollah fighters seized villages while closing in on Qusair itself.
The intensity of the fighting reflects the importance that both sides attach to the area. In the regime's calculations, Qusair is strategically located between Damascus and the Alawite heartland near the Mediterranean. For the rebels, overwhelmingly Sunni Qusair has served as a conduit for shipments of weapons and supplies smuggled from Lebanon to opposition fighters inside Syria.
A Lebanese official close to Hezbollah told The Associated Press that the death toll figures were "exaggerated." He added, however, that 14 Hezbollah members from southern Lebanon were killed in the fighting Sunday, adding that some of the fighters' bodies were still in Syria. He spoke on condition of anonymity for fear of reprisals from Hezbollah, which maintains a shroud of secrecy on its security operations.
Evidence of the group's heavy involvement in Syria was on full display Monday.
In the town of Nabi Sheet in eastern Lebanon's Bekaa Valley, a Hezbollah stronghold, about 2,000 people attended the funeral of Hassan Shukur, an 18-year-old Hezbollah fighter.
Hezbollah comrades fired in the air in mourning and played the group's funeral march as they carried Shukur's coffin draped in a yellow Hezbollah flag through the streets at his funeral attended by senior members of the group.
"We will fight in all of Syria because we are fighting the Israeli enemy," said Sheik Mohammed Yazbeck, a member of Hezbollah's highest decision-making body, the Shura Council.
Shukur is the son of a Hezbollah official and a nephew of the head of the Lebanese branch of Syria's ruling Baath Party. He was among several group members who were buried Monday.
The funeral in Nabi Sheet marked a rare acknowledgment by the group of its direct involvement in the Syria fighting.
In recent weeks, the group has held several low-key funerals in Lebanon for gunmen who it said were killed while "performing their jihadi duties," without saying where or how they were killed.
In a sign of solidarity, Syria's Grand Mufti Ahmad Badreddine Hassoun, the country's top state-appointed Sunni Muslim cleric and an Assad loyalist, toured the families of slain Hezbollah members in south Lebanon on Monday.
On the mountain road linking Beirut with the Syrian border, ambulances carrying paramedics from Hezbollah's Islamic Health Organization raced up and down the motorway, apparently bringing the group's casualties into Lebanon.
Lebanese security officials said about 300 paramedics had undergone intensive training recently by Iranian experts in the Bekaa Valley on how to evacuate wounded fighters involved in street battles. The officials spoke on condition of anonymity because they were not authorized to give official statements.
In Hezbollah's stronghold south of Beirut, people were urged through Shiite mosque loudspeakers to donate blood at the nearby Rasoul al-Azam hospital. In the southern market town of Nabatiyeh, residents were called upon to donate blood at the group's Ragheb Harb hospital in the nearby village of Toul.
Former Prime Minister Saad Hariri, a top Sunni Lebanese leader, accused Hezbollah of "leading Lebanon to the abyss."
The fighting in Qusair sparked battles between Sunni gunmen and Alawite fighters in Tripoli, Lebanon's second-largest city, that left at least two people dead and 26 wounded, Lebanese security officials said.
Regime troops and Hezbollah fighters, who laid siege to Qusair weeks ago, launched an offensive to regain control of the town, with Hezbollah's fighters advancing from the east and south, a Syrian opposition figure said.
He added that it took Hezbollah troops a few hours to take control of the town's main square and municipal building. By the end of the day Sunday, they had pushed out rebel units, including the al-Qaida-affiliated Jabhat al-Nusra, from most of Qusair, he said Monday, speaking on condition of anonymity for fear of retaliation by both sides.
He said fighting was focused in the northern part of the town on Monday.
The account matched that of Syria's state news media, which said Assad's troops took control of most of Qusair on Monday. State-run TV said forces restored stability to the entire eastern front of the town, killing scores of "terrorists" the term used by the Syrian regime to refer to all rebels.
An official in the Homs governor's office told the AP that more than 60 percent of the city is in government hands after scores of gunmen were killed or surrendered Sunday. The official, who spoke on condition of anonymity because he was not allowed to give information to the media during an ongoing military operation, said more than 1,500 residents fled the city due to intense fighting.
Qusair-based opposition activist Hadi Abdullah denied official reports that the army was advancing in the town, saying they were still trying to storm it.
"They go in and out. Until now I can say with confidence that they have not been able to enter the town and stay there," Abdullah said.
An amateur video released by rebels showed the body of a bearded dead man with a tattoo of a Shiite saint on his arm.
A local commander who was identified as Muwaffaq Abul-Sous said: "We the people of Qusair have decided to make the city Hezbollah's graveyard." He added that rebels killed about 30 Syrian soldiers and Hezbollah fighters. The video appeared consistent with AP reporting.
Ibrahim Bayram, an expert on Shiite affairs who writes about Hezbollah for Lebanon's An-Nahar newspaper, said the group has decided to join the battle in Syria "having calculated the results."
"It is a strategic decision for Hezbollah, which sees the battle in Syria as part of its own battle against Israel," he said.