Members of Libya's minority Berber, or Amazigh, community have stormed the parliament building in Tripoli.
A spokesman for the General National Congress (GNC) said windows were smashed, furniture destroyed and documents belonging to deputies stolen.
There were no reports of any injuries after the incident, which happened during a break in a regular session.
The Amazigh were demanding that the future constitution recognise their language, ethnicity and culture.
Though they make up just 5-10% of Libya's six million population, Amazigh predate the Arab settlers who brought Islam with them from the east.
They suffered decades of repression and discrimination during the rule of Muammar Gaddafi, who was overthrown during an uprising in 2011.
Gaddafi saw Amazigh as a threat to his view of Libya as a homogenous Arab society. The Amazigh language and script Tamazight, which is distinct from Arabic, were officially banned and could not be taught in schools. Giving children Amazigh names was forbidden.
Amazigh fighters played an important role in the armed rebellion against the Gaddafi regime. One of the main fronts was in the Nafusa Mountains, where the population is predominantly Amazigh.