"It is doubtful that they have acted on their own ... it appears that a power above them pressured them to play a role in the planning and execution of the assassination," Prime Minister Fouad Siniora was quoted as saying in Beirut's daily As-Safir.
"Is that power a Lebanese one receiving orders from outside, or the orders came directly from outside, this needs to be established by the investigation," Siniora said.
He was apparently suggesting a possible role played by Syria, which ruled Lebanon by proxy for years until it pulled out its military and intelligence forces last April, almost two months after Hariri's Feb. 14 assassination in a massive Beirut blast.
Lebanon's former security chiefs, Jamil Sayyed of general security, Raymond Azar of military intelligence and Ali Hajj of the internal security forces, in addition to Mustafa Hamdan, commander of the Republican Guards, were arrested last week as suspects in the planning of the assassination. They are all close to President Emile Lahoud.
Siniora also advised Lahoud, a pro-Syrian, not to travel to New York this month to participate in meetings at the United Nations in view of the suspected involvement of his men in Hariri's slaying.