An elite Libyan unit joined a renegade general to battle Islamists in the east as rising lawlessness in the nation's two largest cities edges it closer to civil war.
The government posted an open letter on its website suggesting that the General National Congress or parliament "take a recess" as a way out of the crisis.
Gunmen stormed the GNC in southern Tripoli on Sunday, two days after an anti-Islamist offensive launched by a rogue general in the eastern city of Benghazi.
Colonel Wanis Abu Khamada, respected commander of an elite army unit, announced on Monday that his troops would join retired general Khalifa Haftar's operation targeting Islamist militias in the North African nation's second city.
Abu Khamada said his unit would join the operation "launched by the Libyan National Army with all our men and weapons".
His forces have come under regular attack in Benghazi by presumed Islamist militias, and dozens of his men have been killed.
With the interim authorities failing to build a regular army and police, militias have ruled the roost since ousting long-time dictator Moamer Kadhafi. It was in Benghazi that the uprising erupted in 2011.
After Sunday's attack on parliament, a colonel claiming to speak on behalf of the army declared that the GNC had been suspended.
The government had no immediate comment but on Monday suggested the GNC "take a recess after the vote on the 2014 budget and until new parliamentary elections" within three months to avoid civil war.
Justice Minister Salah al-Marghani said two people were killed and 55 wounded in Sunday's clashes between rival militias in southern Tripoli but that the violence had "no real link" to events in Benghazi.
Witnesses said the Tripoli assailants belonged to the powerful Zintan brigades that have attacked the GNC in the past.
The Zintan brigades control areas in southern Tripoli around the airport.
MPs were evacuated as heavy gunfire erupted after a convoy of armoured vehicles headed for the GNC.
Gunmen set fire to an annex of the parliament building before withdrawing towards the airport.
Militias have launched several attacks on the GNC, including on March 2 when two lawmakers were shot and wounded.
The Tripoli violence came two days after fierce fighting killed 79 people in Benghazi, where Haftar unleashed his so-called National Army on Islamist militias, backed by air power.
Also on Sunday, armed Islamists attacked Benghazi's Benina air base but no one was hurt, its commander said.
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- 'We will return' -
Haftar, accused by Tripoli of staging a coup, has said he is preparing a new assault, vowing to eradicate "terrorism".
"Each battle is followed by a regrouping of units. And we will return in force," he said.
Haftar, who led ground forces in the 2011 revolution, said: "Our operation is not a coup and we do not plan to seize power."
Haftar shares the Zintan militias' hostility towards the interim parliament, saying he does not recognise the GNC whose "mandate has already expired and who are rejected by the people".
The interim parliament -- in which Islamists are strongly represented -- sparked outrage earlier this year when it extended its own mandate until December.
The regular army says Haftar is backed by tribes, army defectors and former rebels who oppose the interim authorities.
His forces in Benghazi on Friday mainly targeted Ansar al-Sharia, designated by the United States as a terrorist group.
In the face of the growing anarchy, Saudi Arabia on Monday closed its embassy and evacuated diplomatic staff.
US ambassador Deborah Jones who arrived in Libya in mid-2013 left the country on Sunday, an airport source said, but she said she was "on family travel" on her Twitter account.
State Department spokeswoman Jen Psaki said Washington was closely monitoring the upsurge of violence, but had not decided yet whether to order the closure of its embassy.
The European Union has said it was "deeply concerned" by the violence.
It urged "all parties to build consensus so as to ensure a transition to a stable democracy", said foreign affairs chief Catherine Ashton's spokesman.
Oil prices were mixed Monday amid the escalating violence in crude producer Libya, analysts said.
The US benchmark, West Texas Intermediate for delivery in June, rose 59 cents to $102.61 a barrel.
Brent North Sea crude for delivery in July dipped 38 cents to stand at $109.37 a barrel in late London deals and compared with Friday's close.