Libyan rebels have seized control of a key coastal city, the country’s beleaguered government conceded on Tuesday, amid new criticism that the growing role of foreign powers in the chaotic conflict has fueled a sudden escalation in fighting.
Forces loyal to the militia leader Khalifa Hifter swept into the city, Surt, on Monday, days after Turkey announced it was deploying troops to prop up the weak United Nations-backed government.
The fall of Surt is a significant blow to the government, which has been under siege from Mr. Hifter’s forces since April.
In 2016, American warplanes carried out hundreds of airstrikes against Islamic State fighters in Surt, in support of a government force that eventually expelled the group from the city. Now that the government has relinquished that gain, this time to Mr. Hifter’s forces, its authority has shrunk to a 250-mile strip of coastline stretching from either side of the capital, Tripoli.
The fall of Surt comes as foreign powers intensify their involvement in the conflict, escalating the battle for control of the country.
If Mr. Hifter can hold Surt, analysts say, his forces could stretch government forces even thinner by drawing fighters away from the defense of Tripoli.
Mr. Hifter, 76, commands his self-styled Libyan National Army from his stronghold in Benghazi, in eastern Libyan. In a country with a bewildering array of rival militias, Mr. Hifter has emerged in recent years as the main challenger to the Tripoli government.