The Amazigh, or Berber, people were stunned when the country's new interim government was announced Tuesday and none of the 26 ministerial posts went to one of their own.
They say they make up around 10-15 percent of the population and played an important role in the rebellion that toppled dictator Muammar Gaddafi.
"We do not recognize this government, and all Libyans must know that we are a part, a powerful and effective part of the country," said Mohammed Kaabr, a doctoral student and part of a delegation that spoke to Prime Minister Abdurrahim El-Keib.
Protesters chanted "Where is El-Keib?" and "There is no difference between Amazigh and Arab!" on the steps of Keib's office while talks went on inside. Kaabr said the meeting was cut short so Keib could try to calm the boisterous crowd.
Amazigh are seeking recognition of their language and culture. Their demands are causing tensions with the Arab majority.
The dispute is one of dozens in Libyan society that have come to the fore since the end of Gaddafi's 42-year rule, making it difficult for Libya's new leaders to govern.
"In Switzerland, there are four official languages. One of them is spoken by 0.5 percent of the population," said Abdul Salam Saki, a petroleum engineer
from the coastal town of Zuara, near the Tunisian border, denouncing Arabic's hegemony in Libya.
Protesters, many of them waving the yellow, blue and green Amazigh flag, shoved their way past security guards into the car park in front of the prime minister's office.
They stopped at the front door of the building, where a group of security guards prevented them from going in. The crowd grew increasingly loud until Keib emerged and spoke through a megaphone, but he was drowned out by chants of "Go home!."
When he returned inside, some demonstrators argued with guards and tried to push their way inside, but the scuffles soon ended and the crowd dispersed.
"They have given enough blood. They have given everything for Libya," Suleiman Dogha, a prominent Amazigh politician, said of the protesters and
Libya's Amazigh played a big part in the uprising against Gaddafi, and their militias now control several districts of the capital. They are one of dozens
of interest groups expressing demands, some of them showing little regard for public order.
Saturday night, a crowd of people from the Souq al-Juma district of Tripoli briefly surrounded a Tunisian passenger jet at an airport in the city, delaying take-off by several hours.
They were demanding a government investigation into the deaths of several fighters from the local militia. Tunisian operator Tunisair later said it was suspending its flights to Tripoli in light of the incident.
Keib had said he would pick a "technocratic" government of experts, based on competence rather than politics, and assured the country that all regions would still be represented.
When the Amazigh balked at the cabinet line-up, the head of the National
Transitional Council, which had the final say in the appointments, said they
should be pleased one of their own had been selected as the country's top
Keib, who returned to Libya after years working as an academic in the United States, has impressed many people with his direct form of communication, oftenleaving his office to talk to disgruntled groups protesting outside.
Many of Libya's strongmen have stayed out of this caretaker government, biding their time until elections due next year. Having little with which to placate the angry crowd, Keib's common touch did nothing to soothe the Amazigh protesters.
"He is a nice man," Kaabr said after the meeting inside, "but it's clear that the power does not lie with Keib."
(Additional reporting by Mohammed al-Kikly in Tripoli and Tarek Amara in Tunis; Writing by Christian Lowe and Francois Murphy; Editing by