The announcement came after a Monday televised speech in which Hizbullah head Hassan Nasrallah provided "proof" that Israel was responsible for Hariri's death.

"The office of the prosecutor has always invited and continues to invite anyone who has evidence relevant to the attack against former prime minister Rafik Hariri to bring it to its attention," tribunal spokeswoman Fatima Issawi told AFP.

In his speech on Monday, Nasrallah set forth a theory that Israel secretly killed Hariri, implicating Hizbullah and Syria for involvement in the murder, in order to cause Syrian troops to leave Lebanon.

As proof of his theory, Nasrallah produced a tape of a man named Ahmed Nasrallah, who had been arrested in 1996 for allegedly spying for Israel. “I met someone who worked with Rafik Hariri and I told him that Hizbullah wants to kill him (Hariri),” the man was heard saying in the tape, referring to an apparent attempt to turn Hariri against Hizbullah.

The Hizbullah chief, according to Walla, said the alleged spy escaped to “occupied Palestine” and was still there, allegedly enlisting Lebanese to collaborate with Israel.

Nasrallah’s speech came amid growing expectations that the international tribunal investigating the 2005 assassination will hold Hizbullah culpable.

A senior Israeli official dismissed Nasrallah’s charges as laughable.

Herb Keinon contributed to this report