Armed groups attacked Libya's interim parliament and an air base in the east, adding to turmoil in the troubled country where a rogue general has launched an offensive against Islamists in the city of Benghazi.
A colonel claiming to speak on behalf of the army declared that parliament had been suspended.
"We, members of the army and revolutionaries (former rebels), announce the suspension of the General National Congress," said Mokhtar Fernana, reading out a statement broadcast on two private television channels.
Private television channel Libya International was hit by rockets, shortly after broadcasting the statement.
"At least four rockets struck the channel's offices. There was material damage but no victims," said a journalist speaking on condition of anonymity.
Since the toppling of dictator Moamer Kadhafi in 2011, successive Libyan governments have struggled to impose order as heavily armed former rebel brigades have carved out their own fiefdoms.
Justice Minister Salah al-Marghani said two people had been killed and 55 wounded in clashes between rival militia groups in southern Tripoli, but he added that the violence had "no real link" to an offensive launched Friday by ex-general Khalifa Haftar against Islamists in Benghazi, 1,000 kilometres (620 miles) to the east.
Witnesses identified the assailants as members of the influential Zintan brigades who are known for their opposition to the Islamists and have attacked parliament, known as the General National Congress, before.
MPs were evacuated from the building in southern Tripoli as heavy gunfire erupted after a convoy of armoured vehicles entered the city from the airport road and headed for the GNC.
Residents said gunmen in civilian clothes attacked the building but no casualties were reported.
The Zintan brigades are made up of former rebels who fought Kadhafi.
The groups from Zintan now control areas in southern Tripoli around the airport.
An AFP photographer said a column of smoke billowed over the GNC building after gunmen set fire to an annex, and that several cars parked nearby had been damaged.
Later, the gunmen were seen withdrawing to their bases and gunfire was heard along the airport road, residents said.
Militias have launched several attacks on the GNC, including on March 2 when two lawmakers were shot and wounded.
The latest violence in Tripoli came after deadly fighting in Benghazi, where Haftar unleashed his so-called National Army on Islamist militiamen on Friday, backed by warplanes.
At least 79 people were reported killed in the Benghazi unrest.
On Sunday armed Islamists attacked the Benina air base in Benghazi but no one was hurt, base commander Colonel Saad Al-Werfalli told AFP.
Signup to our newsletter and follow us on Facebook and Twitter!
"Rockets are being fired at the base, but so far it's not serious," Werfalli said, adding that the rockets hit waste land.
- New Benghazi assault planned -
In Benghazi, the retired general accused by Tripoli of staging a coup has said he is readying a new assault on Islamist groups, vowing to eradicate "terrorism".
"Each battle is followed by a regrouping of units. And we will return in force," Haftar said after his men withdrew late Friday.
The government accused the "outlaw" Haftar of trying to mount a coup and declared a Benghazi no-fly zone.
Haftar, who led ground forces in the 2011 revolution, said: "Our operation is not a coup and we do not plan to seize power."
The general defected from Kadhafi's forces in the late 1980s and spent nearly 20 years in the United States before joining the uprising.
Detractors accuse him of being in the pay of the Americans.
Nuri Abu Sahmein, speaker of the GNC, Libya's highest political body, has denounced the Benghazi operation and speculated that Haftar was behind Sunday's attack on parliament.
It is "an action outside state legitimacy and a coup d'etat", said a joint statement read on state television by the GNC chief, flanked by newly-appointed Prime Minister Abdullah al-Thani and armed forces chief of staff Abdessalam Jadallah al-Salihin.
"All those who took part in this coup bid will be prosecuted."
Haftar responded by saying he does not recognise the GNC whose "mandate has already expired and who are rejected by the people".
The interim parliament sparked outrage earlier this year when it extended its own mandate from February until December.
Subsequent protests compelled it to promise early elections and a new electoral law.
Ex-rebels, particularly Islamists, have been blamed for attacks that have killed dozens of members of the security forces, judges and foreigners in Benghazi, cradle of the revolution.
The army says Haftar is backed by tribes, army defectors and former rebels who oppose the central government.
Haftar's forces on Friday mainly targeted Ansar al-Sharia, an organisation designated by the United States as a terrorist group.
His offensive comes at a time of high political tension, particularly after this month's disputed election of the Islamist-backed Thani.