One policeman was killed in the Beirut clashes, while dozens of protesters were wounded.
Lebanese authorities have taken into custody 19 people as part of an investigation.
US President Donald Trump says he will join a conference call to discuss aid to Lebanon.
At least 158 people were killed in the explosion and more than 6,000 others injured, but numbers are expected to rise as search and rescue operations continue for missing people.
Prime Minister Hassan Diab has called for early polls, saying it is the only way out of the country's crisis.
In a national address, the premier said he will introduce a draft bill proposing early elections as thousands of angry protesters took to the streets.