The UN report, submitted on Thursday to the Security Council, cited Ahmad Abd al-Al, a member of a pro-Syrian Muslim group, and his brother Mahmoud Abd al-Al, for their suspected involvement in the 14 February assassination, which has transformed Lebanon's political landscape and prompted Syria to end its 30-year-old military presence there.
Ahmad Abd al-Al, of the Ahbash group, was a key figure in the plot, according to the report.
His brother called the mobile phone of President Emile Lahoud shortly before the blast that killed al-Hariri and 22 others near Beirut's seafront, the report added.
Lahoud's office has strongly denied the call.
The move by public prosecutor Said Mirza brings the number of people charged in connection with the murder to 11.
The UN investigation led by German prosecutor Detlev Mehlis has named senior Syrian officials, including the brother-in-law of President Bashar al-Assad and their Lebanese allies, as suspects in the killing.
Syria has repeatedly denied any role but was forced to bow to world pressure and withdraw its troops from Lebanon in April after mass protests in Beirut.
Syria has dismissed the Mehlis
report as politically motivated
The Mehlis report cited Ahmad Abd al-Al, a member of the Ahbash group in Lebanon with strong historical ties to the Syrian authorities, as a significant figure in the assassination plot, as he had used his mobile phone with "all the important figures in this investigation".
There were numerous contacts between Abd al-Al and Lebanese state security on the day of the blast, including Brigadier-General Faysal Rashid, chief of state security in Beirut, and others, the report said.
Abd al-Al's brother, Mahmud Abd al-Al "made a call minutes before the blast, at 1247 hours, to the mobile phone of Lebanese President Emile Lahoud", it said.
In the light of the Ahbash connection, Abd al-Qadir al-Fakhani, press officer of the group in Lebanon, was interviewed on Aljazeera last Thursday.
He said the Mehlis report neither implicated Abd al-Al nor the Ahbash group. "We should not be accused. We reject these terrorist activities. We hope the report would present answers for those who want the truth, not for those who want fabrication and false accusations."
Mere phone call
Al-Fakhani said the Mehlis report did not accuse Abd al-Al of anything, but merely mentioned a phone call between him and the Lebanese president [Emile Lahoud].
Abd al-Qader al-Fakhani: Mehlis'
report does not implicate Ahbash
"Ahmad Abdel-Al, as the person in charge of public relations of Ahbash group, had phoned some Lebanese officials, particularly security officials, for help in fathoming the truth about who killed al-Hariri," he said.
"First, the Lebanese presidency has denied any phone call between President Lahoud and Ahmad Abdel-Al a few minutes before the assassination," al-Fakhani said.
"Second, even if the phone call had been made, does any citizen who calls the president of his country become a killer and a criminal?
Al-Fakhani continued: "This is very odd, to expect our citizens not to call the president or ministers so as not to be labelled killers and criminals."