The Special Tribunal for Lebanon unveiled charges on Monday that widen the investigation into assassination attempts and killings believed to be linked to the 2005 murder of prime minister Rafiq Hariri.
The charges come six years after the last indictment was issued and as the court process into Mr Hariri's murder enters the final stages.
Pre-trial judge Daniel Fransen lifted the confidentiality of his decision confirming the new charges against Salim Ayyash.
They relate to the assassination of former Lebanese Communist Party secretary general George Hawi in a car bombing in June 2005.
They also concern the attempted murders of Lebanese politicians Elias Al Murr in July 2005 and Marwan Hamadeh in October 2004.
Mr Ayyash is one five members of the Lebanese group Hezbollah who have been charged over Hariri's killing, all of whom are being tried in their absence.
The new charges against him include assassination attempts on 19 people.
There were a string of car bombings in Lebanon against anti-Syrian journalists and politicians about the time of Hariri’s death, which led to the withdrawal of Syrian troops after 29 years of occupation.
Mr Ayyash is charged with “conspiracy to commit terrorism” in the Hariri case and is being defended by a publicly appointed lawyer.
Hezbollah, a Damascus ally, has rejected the accusations against its members, arguing there is a lack of solid evidence, and has refused to hand over the suspects.
The militant group is also a political party in Lebanon but is classified as a terrorist organisation by the US.
Based in The Hague, the tribunal was set up in 2009 at the request of the Lebanese government to prosecute crimes related to the February 14, 2005 bombing that killed 22 people, including Hariri, and injured at least 230 others.
The tribunal's hearings began in 2014 and concluded in September 2018. Lebanese media reported that a final verdict was expected next month.
The tribunal said on Monday that there was enough evidence against Mr Ayyash to merit a trial on the new charges.
It issued new warrants for his arrest to the Lebanese government and international police organisations.
"The new indictment is an additional element to fuel accusations against Hezbollah," Lebanese political analyst Sami Nader told The National.
"The fact that the group refuses to hand Ayyash over points to the fact that it played a role in Mr Hariri’s death."
Prosecutors say Hariri’s assassination was organised by Mustafa Badreddine, with Mr Ayyash as his immediate subordinate.
The two men, along with Hussein Oneissi and Assad Sabra, were first indicted in 2011. Charges against Mr Badreddine were dropped after his death in Damascus in 2016.
In 2013, a fifth man, Hassan Merhi, was indicted.