The outlawing of public demonstrations by the government, is the first response to the death of former prime minister Rafik Hariri.
The protesters are calling for a withdrawal of Syrian troops and for the Syrian-backed government to resign. Hundreds of people are demonstrating peacefully, lighting candles and praying at the grave of Hariri, where the bible and holy koran lie side by side.
As the ban on protesting became public, security officials cordoned off downtown Beirut in a move to contain the protesters. Lebanon's interior minister ordered troops to "use all necessary means" to stop all demonstrations in the city.
An investigation into the assassination of Hariri is being carried out in Beirut by a team from the U.N.