A UN-backed tribunal into the assassination of former Lebanese prime minister Rafiq Hariri in a huge car bombing in 2005 will deliver its long-awaited verdict on August 7, the court announced on Friday.

Billionaire Hariri, who was Lebanon's Sunni Muslim prime minister until his resignation in 2004, was killed in February 2005, when a suicide bomber detonated a van next to his armoured convoy on the Beirut seafront.

Another 21 people were killed and 226 injured in the assassination, with fingers pointing at Syria which had long been a power-broker in the country.

The Netherlands-based court said it "issued a scheduling order today for the public pronouncement of the judgment" in the case against four suspects from Lebanon's Shiite Muslim fundamentalist group Hezbollah, who are being tried in absentia.

Due to the coronavirus pandemic, the hearing "will be delivered from the courtroom with partial virtual participation", it said in statement.

The tribunal was created by a 2007 UN Security Council resolution at Lebanon's request, and the four defendants went on trial in 2014 accused of core roles in the attack.

Salim Ayyash, 50, is accused of leading the team that carried out the bombing, while Assad Sabra, 41, and Hussein Oneissi, 41, allegedly sent a fake video to the Al-Jazeera news channel claiming responsibility on behalf of a made-up group. 

Hassan Habib Merhi, 52, is accused of general involvement in the plot.

The alleged mastermind, Hezbollah commander Mustafa Badreddine, was indicted by the court but is now believed to have died while leading the militia's forces fighting with the Syrian regime in May 2016.

Hezbollah chief Hassan Nasrallah has refused to hand over the suspects and warned the tribunal "don't play with fire" while Syrian leader Bashar al-Assad says it is a tool to "pressure Hezbollah".