Hezbollah is vowing to take revenge after one of its top terrorist leaders was killed.

The threat against Israel came during a massive funeral for the man known as "the first Bin Laden."

Tens of thousands of people poured into the streets of Lebanon to honor Imad Mughniyeh

He was killed yesterday in a bombing and his followers blame Israel for his death.

It's still unknown who was behind the assassination of Hezbollah's chief terrorist mastermind. But the group's secretary general pointed a finger squarely at Israel today during a funeral rally to commemorate Mugniyeh.

"Just one word. Given this killing, the time, place and style, Zionists, if you want this kind of open warfare, then let the whole world listen: let it be open warfare," said Hassan Nasrallah, Hezbollah leader.

Nasrallah spoke via satellite from a secret location to a large crowd in southern Beirut. He threatened retaliation against Israel, although Israeli leaders have denied any involvement in the car bombing that killed Mugniyeh yesterday in Damascus.

Mugniyeh -- who was behind the deaths of hundreds of Americans over the past three decades -- was given full military honors as his coffin passed through the streets of southern Beirut.

Just a few miles away, another huge rally was held opposing Mugniyeh's allies Hezbollah, Syria and Iran. The demonstration marked the three-year anniversary of the murder of Lebanese Prime Minister Rafiq Hariri. Syria is widely suspected of being behind Hariri's death.

The two funerals highlighted the deep divisions within Lebanon, due in part to foreign meddling.

Perhaps to underscore that point, Iran's foreign minister appeared at Mugniyeh's funeral as a show of support for Hezbollah.