Large crowds rallied outside the government building and on Banks Street after heeding a call for action spread on social media.
Dozens of youths set fire to tire piles, blocking a busy traffic tunnel that leads to the central Hamra street.
Demonstrations prompted by fears of a nearing economic collapse were also held in the northern town of Hermel and in the city of Baalbek farther south.
A nationwide strike last week shut 97 percent of gas stations, whose owners said they needed more dollars to pay fuel distributors. The national miller association warned of a grain shortage for the same reason.