Hezbollah chief Hassan Nasrallah said his Shiite militant group is not seeking confrontation with Israel.
Israel launched air raids against Syrian army positions early Wednesday and issued a stark warning to Damascus just hours after a bomb on the occupied Golan Heights wounded four of its soldiers.
Syrian regime forces were Monday readying an assault on the last rebel-held areas in the Qalamoun mountains, strategically located on the Lebanese border, after overrunning key opposition bastion Yabrud.
Moscow accused Washington of prolonging the Syrian conflict by supporting the opposition ahead of a UN Security Council vote Saturday that threatens to further deepen big power divisions.
The chief of Lebanon's Shiite movement Hezbollah, Hassan Nasrallah, vowed on Sunday that the group would prevail against extremists fighting in neighbouring Syria.
Hezbollah on Wednesday said one of its leaders had been assassinated near Beirut and accused Israel, the Lebanese Shiite movement's arch-foe, of being behind the killing.
Streets leading into powerful Hezbollah's stronghold in the southern suburbs of the Lebanese capital have been cordoned off, as guards in civilian clothes search a long line of cars.
A huge car bomb blast killed at least 18 people Thursday in a densely populated Beirut bastion of Lebanon's Shiite group Hezbollah, a military backer of Syria's embattled President Bashar al-Assad.
President Barack Obama announced Monday he had extended for at least a year the US freeze on financial assets of entities linked to Hezbollah, citing a threat to Lebanon's stability.
Shiite Iran has denounced the European Union for its decision to blacklist Hezbollah's armed wing as a terror group, accusing it of acting in Israel's interests.
The European Union on Monday put the military wing of Lebanese Shiite group Hezbollah on its of terrorist organisations, a move that the group slammed as aggressive and unjust.
EU foreign ministers decide Monday whether to blacklist the military wing of Lebanon's Hezbollah group, with an eye also on the conflict in Syria and the possible resumption of stalled Israel-Palestinian talks.
A year after an anti-Israeli bus bombing killed six people, Bulgaria is struggling to identify the attacker or confirm his suspected links to Hezbollah or Iran.
The United States on Monday led western calls for tougher UN action on Iran's arms supplies to Syria and its Lebanese ally Hezbollah.
A Lebanese bank accused of laundering money from drugs and other operations for clients tied to Hezbollah militants agreed Tuesday to pay US authorities $102 million to settle the charges.
Syria's civil war has caused a split within Hamas over whether to cling to Shiite backers Damascus, Tehran and Hezbollah or side with Sunni allies such as Qatar, Egypt and Turkey.
The US on Wednesday condemned a Hezbollah-backed assault on the town of Qusayr, as France kept up the pressure for action over what it said was the regime's use of sarin gas.
The United States on Thursday accused Iran of sponsoring "terrorism" at a level unseen in decades and said that the separate threat from Al-Qaeda has been significantly degraded.
Syrian President Bashar al-Assad threatened Israel with renewed fighting in the Golan Heights and said Russia was committed to supplying him with advanced missiles.
The United States demanded the immediate withdrawal of Hezbollah fighters from Syria on Wednesday, saying their active role in combat there was an "extremely dangerous escalation."