Hezbollah leader Sayyed Hassan Nasrallah said on Friday that his group would wait for results of an investigation into the Beirut port explosion, but if it turns out to be an act of sabotage by Israel then it would "pay an equal price." 

The leader of the powerful Iran-backed Shi'ite Muslim group said in a televised speech that the two theories under investigation were that either sabotage or an accident due to negligence caused the explosion of warehoused ammonium nitrate. 

Israel has denied any involvement in the August 4 blast that killed at least 177 people, injured over 6,000, damaged swathes of the city and left 300,000 homeless. 

Lebanon's President Michel Aoun has said investigators were looking into negligence, an accident or "external interference." 

Nasrallah, who last week denied accusations that Hezbollah has arms stored at Beirut port, said that among sabotage possibilities were a deliberate fire or the planting of a small bomb. 

"Who could be behind an act of sabotage? It could be this side or that, and it could be Israel, which nobody can deny," he said.

Hezbollah was waiting for the Lebanese probe's results and if it found "this was a terrorist sabotage operation, and that Israel had a role, then not only Hezbollah will respond. The entire Lebanese state ... must respond," he said. "Israel will pay a price the size of the crime if it committed it." 

Hezbollah, which exercises sway over government in Lebanon, has fought many wars with Israel. 

Lebanon's prosecutor general has pressed charges against 25 people, including senior port and customs officials, a judicial source said on Friday.

Read more:

Can Lebanon rise from the rubble?

Nasrallah also called for the formation of a national unity government days after Prime Minister Hassan Diab's cabinet resigned amid fury over the blast. 

Nasrallah dismissed the idea of a "neutral government" as a "waste of time" for a country where power and influence are distributed according to religious sects.  

"We don't believe there are neutral (candidates) in Lebanon for us to form a (neutral) government," he said. Instead, the Hezbollah chief called for a government model that has endured for years, despite prolonged political and economic crises and demands for change. 

"We are calling for attempts to form a national unity government, and if that is not possible, then a government that secures the widest representation possible for politicians and experts," Nasrallah said.  

"We call for a strong government, a capable government, a government that is protected politically," he added.  

A government that does not have the backing of the country's top political blocs "either falls, or collapses, or is toppled in parliament at any given cross roads," he said. 

Lebanon's parliament on Thursday approved a two-week state of emergency in Beirut that grants sweeping powers to the army. 

(With input from Reuters, AFP)