Former Lebanese premier Rafiq Hariri was killed in a massive explosion in central Beirut on February 14, 2005 [AFP]

Lebanese officials are expecting a UN-backed tribunal investigating the assassination of former prime minister Rafik al-Hariri to issue indictments soon.

The officials told Reuters news agency on Tuesday that they anticipated the indictments to be issued this week or next, but gave no details.

The long-awaited indictments are expected to accuse members of Shia group Hezbollah of involvement in the killing, and have already triggered a political crisis which brought down the government of Hariri's son, Saad al-Hariri, in January.

Hezbollah pulled out of Saad al-Hariri's government after he rejected its demands to cut ties with the tribunal, withdraw the Lebanese judges and end Lebanon's contribution to its budget.

The Shia group, which denies any role in the 2005 assassination, resigned from Hariri's unity government just days before the tribunal prosecutor filed his indictments to a pre-trial judge on January 17.

The indictments, twice amended since then, have remained secret while the pre-trial judge assessed whether there was enough evidence to proceed with a trial.

In a statement, the Special Tribunal for Lebanon (STL), based in Leidschendam in the Netherlands, said it had "no comment to make about the content of the indictment".

"The mandate of the STL is of a judicial nature. The integrity of the STL proceedings requires that legal considerations alone determine if and when the tribunal will make any announcement about the completion of the review process," the statement said.

Two pan-Arab newspapers reported that the indictments would be issued "within two days".

One of them, Asharq al-Awsat, said five Hezbollah members would be indicted.

'Judges leave Lebanon'

An official source told Reuters that Lebanese judges who are part of the tribunal had left Lebanon.

Local media said this could be a precautionary move to ensure their safety when the indictments were issued.

Hariri was killed by a huge truck bomb, triggering international condemnation that forced neighbouring Syria to end a 29-year military presence in Lebanon.

Six months after the February 14, 2005, assassination, four pro-Syrian Lebanese generals were arrested at the request of the UN investigator.

A report delivered to the UN Security Council initial findings implicated high-ranking Syrian and Lebanese officials in the murder.

However, the generals were released in 2009 for lack of evidence.

Hezbollah leader Sayyed Hassan Nasrallah has since said that the group expects some of its members to be accused by the tribunal, which it describes as a tool of Israel.