Libya’s militias have captured most government ministries in the capital, Tripoli, the government has said.
Armed men had blocked staff from entering offices, it added in a statement.
On Sunday, militiamen seized the US embassy with videos showing cheering men diving from a balcony into a swimming pool.
Libya has been hit by anarchy since Col Muammar Gaddafi was overthrown by the Nato-backed militias in 2011.
The militias have been fighting for power among themselves since then, with an Islamist-linked group, Libya Dawn, capturing Tripoli last week.
Senior government officials and the elected parliament moved to the eastern city of Tobruk, more than 1,000km (620 miles) away, last month.
“We announce that most ministries, institutions and state bodies in the capital Tripoli are out of our control,” the government statement said.
The US and other countries evacuated their embassy staff in July, as fighting escalated for control of Tripoli.
Libya’s central bank and the state oil company are based in the city.
Prime Minister Abdullah al-Thinni and his cabinet resigned last week so that the parliament, elected in July, could choose a new government.
The elections were the second since Col Gaddafi was killed in the 2011 revolution, but hopes that the polls would help restore stability in Libya have failed to materialise.
Battle for Libya:
Misrata-led alliance (Libya Dawn):
- Effectively in control of Tripoli
- Includes some Islamist militias, such as LROR
- Also Libya Central Shield
- Called on former parliament, GNC, to reconvene
- Had controlled Tripoli airport for three years
- Includes al-Qaqa Brigade and al-Sawaiq Brigade
- Al-Qaqa had officially joined the national army but remained autonomous
- Supports new parliament
- Loosely allied with rogue General Haftar
Why is Libya lawless?
Guide to Libya’s militias