Hassan Nasrallah, the leader of Hezbollah, has criticised the international investigation into the 2005 asssassination of Rafiq al-Hariri, Lebanon's former prime minister.

Nasrallah said on Friday that a decision by a UN-backed court to free Lebanese officers held over the murder does not mean the tribunal is "honest" and instead "is proof that...their detention was political."

He also called on Lebanon to widen its investigation into the assassination to include the possibility of Israeli involvement.

"Whoever says that Israel did not have the motive or interest in killing al-Hariri would be killing al-Hariri a second time," he said.

Suspects release

The UN-backed Special Tribunal for Lebanon ordered the release of four Lebanese officers who are considered to be pro-Syrian on Wednesday, saying there was not sufficient evidence to keep the charges.

The officers, widley seen as symbols of Syria's domination over Lebanon at the time of the killing, were among several other Syrian and Lebanese officials listed as potential suspects in a preliminary report by the international investigation.

Nasrallah insists that the release of the officers proves that the international investigation was false and politically motivated.

"I hope that nobody will ask us in advance to accept anything from the prosecutor, or the international investigation, or the judges of the tribunal simply because it issued a correct decision two days ago," he said.

Syria has been blamed by many for al-Hariri's murder, although Syria's government has repeatedly denied the allegations. But just two months after the assassination, Syria pulled all of its troops from Lebanon, ending a nearly three decade military presence in the country.

The release of the four officers was announced just under one month before Lebanon's parliamentary elections on June 7, which will see al-Hariri's son, Saad, up against the Hezbollah-led alliance.