An armed militia has attacked the Tunisian general consulate in Libya's capital and taken 10 employees hostage.
Tunisia's Foreign Ministry condemned the attack, calling it "a vile aggression" against the country's sovereignty and a violation of international conventions protecting diplomatic personnel.
Tunisia's government is monitoring the situation and working to secure the release of the employees, a statement said.
Libya has been divided between rival governments and hundreds of militias in the aftermath of its 2011 civil war that ousted dictator Muammar Gaddafi.
An Islamist-led government backed by militias seized Tripoli last August. Libya's internationally-recognised parliament, which was forced out, convenes in the eastern city of Tobruk.
The ministry repeated a warning to Tunisians urging them not to travel to the neighbouring country under the current instability.
Official figures say some 60,000 Tunisians are working in Libya.