Lebanon's state electricity company said on Saturday that its power plants had stopped working after protesters stormed a key substation and tampered with the electrical equipment, AFP reported.
Demonstrators angered by ongoing blackouts stormed an Electricite du Liban substation in the Aramoun region north of Beirut on Saturday, EDL said in a statement.
"Protesters disconnected a 150-220 kilovolt power transformer and opened circuit breakers connecting the Zahrani power plant to the Aramoun station," it said.
"This caused disturbances on the electrical grid... which led to a total blackout across Lebanese territory as of 17:27 (1527 GMT)".
Lebanon has been grappling with round-the-clock power cuts that last at least 20 hours a day due to a financial crisis that has hampered key imports, including fuel for power stations.
Private generator owners have hiked prices and rationed supply in recent months, with costs surging after the government gradually lifted fuel subsidies.
The international community has long demanded a complete overhaul of Lebanon's electricity sector, which has cost the government more than $40 billion since the end of the 1975-1990 civil war.
Lebanon has reached an agreement on bringing Jordanian electricity and Egyptian gas into the country via war-torn Syria, while Hezbollah has separately started hydrocarbon deliveries from Iran.
The shipments from Iran are being portrayed as a victory by Hezbollah.
Lebanese Prime Minister Najib Mikati criticized the Iranian fuel shipments imported by Hezbollah, saying they constitute a breach of Lebanon's sovereignty.
The United States has also denounced Hezbollah's deliveries of Iranian fuel to Lebanon as a “public relations stunt” and warned that Tehran remained under sanctions.