The new all-day curfew starts at 5 am (0300 GMT) on Thursday and ends at 5 am on January 25, a statement by the Supreme Defense Council said.
Lebanon last week ordered a three-week lockdown until February 2 that included a nighttime curfew from 6 pm to 5 am.
But tighter measures were now necessary as hospitals run out of capacity to treat critically ill patients, President Michel Aoun said in the statement.
“We have seen dreadful scenes of citizens waiting in front of hospitals for a chair or a bed,” he said.
The new measures also include stricter procedures at the airport for passengers arriving from Cairo, Addis Ababa, Baghdad, Istanbul and Adana.
Travelers arriving from these destinations will have to quarantine for seven days at a hotel while all others will quarantine up to 72 hours.
Overall air traffic at the airport will also be cut to 20 percent from normal operating levels and supermarkets will be limited to delivery services.
Anticipation of stricter measures on Monday had driven many Lebanese to wait in long queues in front of supermarkets and empty shelves.
Lebanon registered 3,743 new infections on Sunday, bringing its total to 219,296 cases and 1,606 deaths since February 21.
Adherence to social distancing and other preventive measures has been lax prompting government fears of a significant rise in cases after the Christmas and New Year holidays.
Daily infections reached an all time high of 5,440 on Friday.
“Sadly we are being faced with a frightening health situation,” Caretaker Prime Minister Hassan Diab said.
“The corona pandemic is out of control because of the stubbornness of people and their rebellion against measures we take to protect them from its dangers.”
The lockdown faces resistance amid concerns over soaring unemployment, inflation and poverty.
Lebanon is still dealing with a devastating financial crisis that has crashed the currency, paralysed banks, and frozen savers out of their deposits.
Medical supplies have dwindled as dollars have grown scarce.
Reporting By Maha El Dahan and Laila Bassam; Editing by Toby Chopra
IMAGE: A customer pushes her trolley next to near empty shelves after people hoarded food as authorities are discussing the latest measures to implement to curb the spread of the coronavirus disease (COVID-19), in Beirut, Lebanon, January 11, 2021. REUTERS/Mohamed Azakir