Hassan Nasrallah, the leader of Hezbollah, has blamed Israel for the murder of Rafiq al-Hariri, the former Lebanese prime minister.
In a video address to journalists from an undisclosed location on Monday, Nasrallah said he had evidence to prove Israel's complicity in al-Hariri's assassination in a bomb explosion in Beirut in 2005.
Al-Hariri and 22 others were killed on the Beirut seafront on February 14, 2005.
The assassination sparked an international outcry and led to the withdrawal of Syrian troops from Lebanon.
The murder has been widely blamed on Syria, but Damascus has routinely denied involvement.
"Nasrallah is trying to present credible evidence to convince the Lebanese that Israel, not Syria or Hezbollah, was behind the assassination," Fawaz Gerges, a Middle East analyst, told Al Jazeera.
He "talked about who has the most to benefit from the assassination ... [by trying to] provide a very complex case by drawing a historical link between Israel" and the killing, Gerges said.
Nasrallah said Israel used spying and covert operations to attempt to drive a wedge between Hezbollah and the Lebanese government.
Aaron Klien, a political commentator in Jerusalem, told Al Jazeera that the contents of Nasrallah's rare speech were not surprising.
"This is exactly what everybody in Israel was expecting, which was to use the Jewish state as a scapegoat because he is up against a rock and a hard place," Klein said.
A UN court probing the assassination of al-Hariri is planning to charge Hezbollah members, Nasrallah said in July.
"Hezbollah is trying to dismiss the findings of international investigations. They want to discredit the basic information that investigators had depended on in making their conclusions," Al Jazeera's Rula Amin reporting from Beirut, said.