The controversial accusation unfolded during a two hour presentation beamed live Monday night from a secret location to a room of invited journalists in Beirut. Nasrallah's accusation against Israel comes as the U.N.'s investigation of the murder is winding down with promises of indictments against senior members of Hezbollah.
The most arresting element of Nasrallah's multi-media presentation was what he claimed were sequences of Israeli air force drone video apparently intercepted and decoded by Hezbollah over several years.
This included material which Nasrallah claimed showed that Israel had been conducting detailed aerial surveillance of Hariri's movements around Beirut in the time leading up to the massive car bomb which killed him and 20 others in February 2005.
"What I showed is not absolute proof," the Hezbollah leader admitted during the speech which was broadcast live throughout the Middle East. "But the door should be opened for such an assumption. For five years nobody, not the tribunal or anybody in Lebanon, made one step towards such a theory."
The U.N. tribunal to which he referred is investigating the killing and in a surprising development has announced it will soon hand out several indictments against senior members of Hezbollah.
This has set Lebanese politics on edge and in previous statements Nasrallah lambasted the tribunal and said he would refuse to hand over his men for questioning.
In Israel there has been no official response to last night's speech and accusation. But some analysts have been quick to draw a connection between the forthcoming indictments and Nasrallah's attempt to implicate Israel in Hariri's assassination.
"Next month the U.N. investigation will probably say that Hassan Nasrallah is to blame for Rafiq Hariri's murder and obviously he wants to pre-empt that by pointing a finger at Israel," said Shlomi Eldar, Israeli Channel 10's Arab affairs specialist.
Hariri's killing led to a period of extreme tension in Lebanon. Syria was initially thought responsible and following massive popular demonstrations in Beirut President Assad withdrew his troops from the country.
But the western leaning faction led by Hariri's son Saad was unable to establish full control, and a fragile political calm has only now returned with the help of both Saudi and Syrian involvement. Hezbollah remains a crucial part of the political landscape.
The tribunal's decision to indict Hezbollah leaders threatens to destroy the delicate status quo. Hezbollah has already shown it controls the dominant military force inside the country and has warned rival political factions not to exploit the indictments for their own gain.