One of the congressmen, Abdul Rahman Sweihli, was shot in the leg after protesters opened fire on him inside the building.
As his security detail rushed him out, gunmen opened fire on their cars as they were trying to flee, his son Bashir Sweihli told CNN.
No information about the second lawmaker was available.
A GNC member speaking on Libyan TV said lawmakers continued their evening session despite dozens of protesters surrounding the building and pouring gasoline on the walls before they stormed the building.
Other members of the GNC, the country’s interim parliament, were assaulted, and some of the women members harassed, lawmakers said.
Young men ransacked the building, and parts of it were set on fire, according to witnesses.
Videos posted to social media sites showed a chaotic scene, with young men setting cars and furniture outside the building ablaze.
Public anger has been mounting against the GNC, especially after members voted last December to extend their term in office until the end of this year.
For almost a month, thousands of Libyans have taken to the streets across the country in peaceful demonstrations demanding an end to the GNC’s term.
In response to the rising tensions, lawmakers announced last month that early elections would be held, but a date has not yet been set.
Earlier in the day, anti-GNC protesters blocked off roads close to the building and set tires on fire after reports spread of an attack Saturday night on anti-GNC protesters. That attack included burning down their tent and reportedly kidnapping some protesters.
More than two years after the overthrow of the Gadhafi regime, Libyans have become increasingly frustrated with the state of their country and the performance of their elected officials.
Separately on Sunday, gunmen shot dead a French national in the eastern city of Benghazi.
Local authorities condemned the killing and said the man was an employee of a private French company that was doing expansion work on the Benghazi Medical Center.
The French Foreign Ministry condemned the killing of the man identified as Patrice Real and said the perpetrators must be pursued and punished.
A Libyan soldier was also killed in Benghazi on Sunday when an improvised explosive device detonated under his car, according to the state news agency LANA.
Four unidentified bodies of young men with gunshots to the head were found in a forest east of Benghazi, LANA reported.
Separately, a fifth unidentified body was discovered in al-Jarutha, west of the city.
Violence levels in the city have spiked over recent weeks with assassinations, kidnappings and bombings becoming near daily occurrences in the city that was the cradle of Libya’s revolution.
While no group has claimed responsibility for the rising violence in Benghazi, residents and officials blame the violence on Islamist extremist groups.
Last week security forces found the bodies of seven Egyptian Christians dumped west of the city.