Warplanes attacked Libya's third-largest city of Misurata on Sunday, the first time the industrial port of 300,000 has been struck in an expanding seven-month civil conflict that has already set on fire the country's largest oil terminal.
The three air strikes, launched by forces loyal to the internationally recognised Tubruq-based government of Prime Minister Abdullah Thinni, targeted an air base, the seaport and a steel factory in the city.
"The armed forces chief of staff declared Misurata a military zone and it will be besieged from east and west alongside continuous escalating strikes," Brig Gen Saqr al-Garoushi, commander of the Thinni government's air force, said in a statement reported by Libyan media.
Though Sunday's air strikes reportedly left no casualties and caused little damage, they herald a potentially new phase in the Libyan civil war.
The complicated conflict pits the Thinni government against the self-declared Islamist-leaning authorities in the capital, Tripoli, backed by Misurata and its alliedLibya Dawn militias. The air strikes on the city come amid a push by its militias to seize control of the country's main oil export terminal at es-Sidr, which on Thursday became engulfed in flames due to the fighting.
Thinni government forces, under the command of the controversial Gen Khalifa Haftar, issued a 72-hour ultimatum that expired late Saturday for Misurata to end the assault or face consequences.
"This is a new, dangerous escalation in violence and one that might not end unless Libya Dawn forces stop their offensive on the oil terminals," said Mohamed Eljarh, a Libyan analyst and non-resident fellow at the Atlantic Council's Middle East centre.
"There have been various warnings that the war would get to Misurata if its forces are not reined in and stopped from attacking others but Misurata's forces and leaders never took these warnings seriously."
Libya, which holds Africa's largest oil reserves, has seen production drop from as high as 900,000 barrels per day earlier this year to 350,000 b/d because of the most recent fighting.
The country has been in turmoil since the 2011 Nato-backed war unseated longtime ruler Muammer Gaddafi. Instability caused by tribal, regional and ideological militias deepened in August when Islamist and Misurata militias seized control of the capital after decisively losing June parliamentary elections. They launched an attack on el-Sidr two weeks ago.
By Saturday, fire at the terminal had spread to five of its oil storage tanks, and Libyan authorities called on Italy and the US to help them put out the blaze. Combatants reportedly agreed to a temporary truce on Sunday to let firefighters quell the flames.
Misurata suffered badly during the uprising against the Gaddafi regime, with much of the city destroyed and more than 1,200 residents killed. It has since played an outsized political and military role, dispatching its heavily armed and battle-hardened militias all throughout the country. But Sunday's air strikes mark the first time city itself has been touched by war since Gaddafi's overthrow.
The Thinni government's military commanders have been warning for weeks that they would employ air power bolstered by its UAE and Egypt allies against Misurata.
Mohamed al-Dayri, the Thinni government's foreign minister, on Sunday met with his Egyptian counterpart Samih Shokri in Cairo, where both vowed to counter "terrorist groups" in the region.
UN special envoy Bernardino Leon has sought to bring the two sides to the negotiating table. Libya Dawn's media office called the Sunday's air strikes an attempt to sabotage any talks. Bur Mr Eljarh said the air strikes might serve as "a wake-up call" for Misurata's leaders to embrace dialogue over war.