The Libyan capital's only functioning airport came under siege on Sunday, as fighting broke out hours after the UN mission in the country condemned continued breaches of an arms embargo.
The UN mission in Libya condemned "in the strongest possible terms" the rocket strikes on Tripoli's Mitiga airport, which wounded at least two civilians and damaged a building.
On Saturday, the UN had said it "deeply regrets the continued blatant violations of the arms embargo in Libya".
World leaders met in Berlin this month to try to end the country’s conflict and uphold the 2011 UN Security Council weapons embargo.
At the meeting, they agreed on a permanent ceasefire and steps to dismantle militias and armed groups backing the Tripoli government, while pushing a political process under the UN.
But fighting broke out on Sunday in the Abu Grein region, 130 kilometres west of Sirte.
Libya has been embroiled in chaos since a 2011 Nato-backed uprising that killed longtime dictator Muammar Qaddafi, with two rival administrations now vying for power.
The conflict deepened last year when Field Marshal Khalifa Haftar, who controls much of the south and east of Libya, launched an assault in April to seize Tripoli from the Government of National Accord, and the militias it employs for defence.
The UN mission said the ceasefire was now at risk of collapsing.
"This fragile truce is now threatened by the ongoing transfer of foreign fighters, weapons, ammunition and advanced systems to the parties by member states, including several who participated in the Berlin conference," it said.
On Sunday, Germany's Foreign Ministry voiced concerns about "a series of unconfirmed but credible reports of embargo violations".
Meanwhile, Turkish President Recep Tayyip Erdogan travelled to Algiers for talks with Algerian leader Abdelmadjid Tebboune on Libya's crisis and the January 12 ceasefire, which Moscow and Ankara brokered.
Algeria shares a border with Libya of about 1,000 kilometres.
The UN says the fighting since last April has killed more than 280 civilians and 2,000 combatants, while thousands have been wounded on both sides. More than 170,000 Tripoli residents have been displaced.
The UN is hoping to hold inter-Libyan talks soon in Geneva to save the truce, as its mission in the country warns of "a renewed and intensified round of fighting".
A military commission established at the Berlin summit, comprising five GNA loyalists and five Haftar delegates, has been asked to define ways of making the truce hold.
"What's important now is to achieve a stable ceasefire, which the military committee wants to negotiate in the coming days," the German Foreign Ministry said.
Ankara sent troops "in a training capacity" to support the GNA this month, in a move criticised by European powers and US President Donald Trump.