Protesters in Beirut attempted to storm the Parliament of Lebanon on Tuesday, the same day the country celebrated the passage of 100 years since the declaration of Greater Lebanon by the French mandate authorities.
Some protesters attempted to smash down walls around the building while others managed to break through one gate before they were forced back by police with tear gas.
Activists have blamed the country's entrenched political class for the August 4 explosion of a stockpile of ammonium nitrate that had languished in the port for years.
Violent clashes erupted, with protesters throwing tear gas canisters back at officers. Activists condemned police actions, saying protesters were beaten.
A military vehicle was also called in to deal with the crowds.
Protesters called for a "new Lebanon" without its reviled leaders, urging visiting French President Emmanuel Macron not to cooperate with them.
In the capital's Martyrs' Square, not far from the port, demonstrators one by one took to a stage to make their demands: a secular state, civil marriage, a productive economy.
Waving Lebanese flags and denouncing "corrupt" politicians, others nearby demanded the birth of a new secular state and the end of what they view as a broken political power-sharing system.
"The first century has been nothing but wars, foreign occupation, poverty, corruption, emigration, sectarian divisions, and now this explosion that killed and wounded thousands," said 21-year-old port worker Omar.
"We urgently need to revamp this system," he said, referring to a political arrangement that seeks to share power between Lebanon's myriad religious communities but instead often leads to an endless deadlock.