"It is an important step on the way to achieving justice and uncovering the truth about the ugly crime," said Saad Hariri in an interview with the Dubai-based al-Arabiya television, which is monitored in Beirut.
Hariri was commenting on the questioning of Gen. Jamil Sayyed, former general security director, Brig. Gen. Raymond Azar, former head of military intelligence, Brig. Gen. Ali Hajj, former chief of internal security forces, and Brig. Gen. Mustafa Hamdan, head of the Republican Guards.
The four security officials and a former pro-Syrian legislator, Nasser Kandil, are being interrogated by an international commission led by German prosecutor Detlev Mehlis investigating Hariri's Feb. 14 assassination.
For his part, opposition leader and a former close ally of the late Hariri, Walid Jumblat said "the countdown for unveiling the truth has started."
"The truth will be revealed soon and I expect that big heads in Lebanon and outside Lebanon will roll down," Jumblat said, as quoted by the national news agency ANI.