BEIRUT, Lebanon — Protesters on Tuesday stopped Parliament from convening to discuss a package of controversial laws that critics fear could provide amnesty for past corruption, as crowds blocked roads leading to government buildings and skirmishes broke out with the riot police.

The action comes on the 34th day of widespread antigovernment protests that have both galvanized and paralyzed the country, and the protesters’ success seemed likely to sharpen tensions between the government and the people.

Several lawmakers had said before the Parliament session was postponed that they would boycott the session, but others on Tuesday could not get through the roadblocks on streets surrounding government buildings.

The session had already been pushed back once: Protesters vowed last week to form a human chain to prevent lawmakers from gathering.