THE HAGUE: Eight lawyers representing the four Hezbollah members due to be tried in absentia for the 2005 murder of former Lebanese premier Rafiq Hariri have been sworn in, a UN-backed tribunal said Wednesday.

"All the defence counsel signed a declaration that they will exercise their duties 'with integrity and diligence, honourably, freely, expeditiously and conscientiously'," Special Tribunal for Lebanon (STL) said in a statement.

The Hague-based STL announced early this month that Salim Ayyash, Mustafa Badreddine, Hussein Anaissi and Assad Sabra will be tried in absentia for the massive February 14, 2005, car bombing in Beirut that killed Hariri and 22 others, including a suicide bomber.

The STL sent arrest warrants for Ayyash and the three others to Lebanese authorities in June, and Interpol issued a "red notice" in July.

But the authorities in Lebanon, where the government is dominated by the Iranian- and Syrian-backed Hezbollah militant group, have failed to arrest them.

Ayyash, 48 and Badreddine, 50, face charges of "committing a terrorist act by means of an explosive device" and homicide, while Anaissi, 37, and Sabra, 35, face charges of conspiring to commit the same acts.

Created by a 2007 United Nations Security Council resolution at Lebanon's request, the STL opened its doors in 2009 and is tasked with trying those suspected of responsibility for Hariri's assassination.

Hezbollah, blacklisted as a terrorist organisation by Washington, has denied involvement.