Hassan Nasrallah, the leader of the radical Shiite Hezbollah movement, on Friday ruled out Israel as being behind the killing of the movement's top military commander in Syria.
"We did not find indications that point out that Israel was behind ... our commander's assassination, and although we don't acquit Israel, we are also not accusing it," Nasrallah said in a speech that marks one week since the assassination of Mustafa Badreddine.
Badreddine was killed inside his base near Damascus airport. Hezbollah, which is backed by Iran, has blamed Sunni extremists.
Nasrallah vowed that more of his commanders and militants will be going to Syria and will continue to fight in ongoing battles.
"We have lost a number of martyrs and wounded ... but despite that we along with our allies in Syria are winning and advancing," he said.
"The martyrdom of any of our leaders has not pushed us to leave any battlefield and Badreddine's blood will push us to a bigger presence in Syria," he added.
Hezbollah is currently reeling from losses on the battlefields in neighbouring Syria, where the Shiite movement is backing President Bashar al-Assad.
Sources in Lebanon say Hezbollah has lost at least 1,500 fighters, including many high-ranking commanders, since 2013. In Beirut's southern suburbs, the group's stronghold, martyr posters line the walls of the streets.
Badreddine took over from Imad Mughaniyeh in 2008 as the group's military chief after the latter was assassinated. Jihad Mughaniyeh, the son, was killed last year in southern Syria.
Replacing such leaders is not easy for the movement, and recruitment of youngsters has been stepped up.
"Every day you hear of at least two or three young men, aged not more than 21, who died in Syria. Some days you hear of more," a resident of Beirut's southern suburb told dpa on condition of anonymity.
"You feel people are getting seriously scared of the fate of their sons who are taking part in battles in Syria," the resident said.
Hezbollah's involvement in Syria was made public by Nasrallah exactly three years ago during a speech celebrating the Israeli withdrawal from south Lebanon in 2000.
There are now estimated to be some 5,000 Hezbollah fighters involved in battles across the country.
Iran itself has been sending aid - including weapons, fighters and commanders - to help al-Assad stay in power and push back rebels. Tehran has also been recruiting Afghan Shiite refugees and Iraqi Shiite militias to aid the government.
The civil war in Syria started as peaceful protests against al-Assad's rule but quickly evolved into all-out conflict, now notably along sectarian lines, after the security forces violently crushed demonstrations.
The Iran-Syria-Hezbollah axis has existed since Lebanon's civil war in the 1980s and is based both on sectarian allegiances but also on staunch opposition to Israel.