Hezbollah's increasingly visible support for President Bashar al-Assad and its latest military challenge to Israel has put the militant group on a collision course with domestic opponents who accuse it of dragging Lebanon towards regional conflict.
While still denying it has sent forces to Syria to fight alongside soldiers trying to crush a 19-month-old uprising against Assad, Hezbollah has held a number of public funerals this month for fighters killed performing "jihadi duties".
Security sources said the men were killed on Syrian territory.
Hezbollah's political opponents, who have for months accused it of aiding Assad's forces, have rushed to condemn the group and warned its involvement in Syria could ignite sectarian tension within Lebanon where religious factions fought a 1975-1990 civil war.
In a defiant speech on Thursday night, Hezbollah Secretary-General Sayyed Hassan Nasrallah said the Shi'ite group was not reinforcing its ally in Damascus. But his comments suggested that Hezbollah fighters may have been fighting in border regions of the poorly defined frontier.
He also confirmed that Hezbollah had sent a reconnaissance drone deep into Israeli airspace, further escalating tensions with Israel which has threatened to bomb Hezbollah's patron Iran over Tehran's nuclear programme.
Nasrallah's speech was "aggressive towards all of his opponents in the Arab world, inside Lebanon and Israel", said Nabil Boumonsef, a columnist at the Lebanese newspaper An-Nahar.
"He has put Lebanon and all of us in the eye of the storm," he said, reflecting growing criticism of a group which six years ago was lionised across the Arab world for standing up to Israeli military might in a 34-day conflict.
Hezbollah, Boumonsef said, "will pay the price of this - and also Lebanon as it will deepen the division and fragmentation".
The revolt against Assad has turned into a civil war with sectarian dimensions, largely pitting the majority Sunni Muslims against Assad's minority Alawite community, which is an offshoot of Shi'ite Islam.
Tensions between Sunnis and Shi'ites have been rumbling in Lebanon ever since the end of the civil war, but resurfaced when former Prime Minister Rafik al-Hariri, a Sunni, was killed in 2005. Hariri supporters accused Syria and then Hezbollah of killing him - a charge they both deny. An international tribunal accused several Hezbollah members of involvement in the murder.
But now the sectarian differences which Hezbollah was able to bridge when it played the role of resistance movement against Israel have deepened with its support for Assad.
FOCUS ON ARMS
After the funeral of Hezbollah fighter Hussein Nimr, attended by more than 1,000 mourners in Lebanon's Bekaa Valley this week, former Prime Minister Fouad Siniora, a Sunni and a fierce Hezbollah opponent, said political leaders must take a stand to halt Hezbollah's "slide towards the armed conflict in Syria".
"This military involvement in the fighting ... would expose Lebanon to unforeseen dangers which it cannot bear and would threaten coexistence in Lebanon, as well as Muslims and Arabs, with unprecedented strife," Siniora said.
But Hezbollah is the only faction in Lebanon to retain its heavy weapons and is unlikely to be willing to give these up without a fight. In its strongholds it power is unassailable, even by the Lebanese army. There are mounting calls however for it to put those arms under some form of state supervision.
In September, President Michel Suleiman proposed that Hezbollah's weapons, which include an arsenal of missiles which the group says can strike anywhere in Israel, be put under the command of the Lebanese army.
Hezbollah is not the only force in Lebanon to be drawn into Syria's conflict, in which activists say 30,000 people have been killed in deepening violence.
Arms and fighters have been smuggled across the border to support Syrian rebels, mainly from Sunni Muslim areas in the eastern Bekaa Valley and northern Akkar province.
"Everyone who (who fuels the violence in Syria) is playing with our blood," Boumonsef said, slamming both Assad supporters and opponents in Lebanon but singling out Hezbollah for particular criticism.
"The level of intervention in the Syria crisis differs from one side to the other," he said. "While some offer a supportive environment and maybe help smuggling and other issues, Hezbollah is involved to a greater extent than that."
Prime Minister Mikati, a Sunni Muslim who had close ties to Syria before taking office, has increasingly struggled to insulate his country from the violence raging across the border.
Street fighting has erupted frequently in the northern city of Tripoli, home to an Alawite minority and staunchly anti-Assad Sunni Muslim majority, and fighting has spilled over the border from Syria.
Lebanon's own sectarian faultlines and political divisions have yet to heal, more than 20 years after the civil war ended.
"We are entering a period in Lebanon which could be very violent," said newspaper columnist Sarkis Naoum. "We are living in instability now ... and I am afraid we are heading towards an explosion."