An energy company responsible for about one quarter of Lebanon's electricity supply has turned off its generators.
Karpowership, a Turkish company, says it is owed more than $100m (£71m) by Lebanon and has not been paid in 18 months.
It also faces corruption charges, which it denies, and an ongoing legal fight.
Lebanon is in a major economic and political crisis, and already suffers regular power cuts, with many people relying on private generators.
The country has not had an agreed government in nine months, after the previous administration resigned in the wake of a devastating explosion at Beirut's port.
Hassan Diab is currently serving as caretaker PM. He stepped down after the blast in August but PM-elect Saad Hariri has so far struggled to form a government, leaving Mr Diab in the post until Mr Hariri can take office.
Karpowership - which provides power from two barges - reportedly shut off supply at 0800 local time (0600 BST).
"We deeply regret shutting down and went to great lengths to avoid it," a statement read.
"For 18 months, we have been exceedingly flexible with the state, continually supplying power without payment or a payment plan, because the country was already facing very hard times. However, no company can operate in an environment with such direct and undue risk."
Around 370 megawatts (MW) of power comes from Karpowership. Reuters news agency reports that Lebanon has a total capacity of about 2,200MW, including the barges, but had far greater need for power - with peak demand in 2020 reaching 3,500 MW.
Early this month, a state prosecutor threatened to seize the ships after a local television channel reported corruption allegations relating to a power contract - accusations Karpowership denies. The company has been threatened with a $25m fine, subject to an ongoing investigation.
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