BEIRUT -- Islamic fighters led by al-Qaida's branch in Syria seized almost full control of the northwestern city of Idlib on Saturday, taking over major roundabouts and government buildings in a blow to President Bashar Assad, whose forces rapidly collapsed after four days of heavy fighting, opposition activists and the extremist group said.
Idlib, a major urban center with a population of around 165,000 people, is the second provincial capital to fall into opposition hands, after Raqqa, now a stronghold of the Islamic State extremist group.
Its capture by the Nusra Front underscores the growing power of extremist groups in Syria, who now control about half the country.
Opposition fighters including Nusra have controlled the countryside and towns across Idlib province since 2012, but Assad's forces had managed to maintain their grip on Idlib city, near the border with Turkey, throughout the conflict.
On Saturday, Islamic fighters swept in, taking over key buildings and tearing down posters of Assad.
Videos posted online by activists and the Nusra Front showed a group of heavily armed fighters kneeling in prayer in the city's sprawling Hanana square as others fired their guns in celebration.
The Nusra Front is leading a group of ultra-conservative rebels in a major offensive to take Idlib that began last week.
They include the hard-line Ahrar al-Sham and Jund al-Aqsa groups, and a few smaller groups loosely affiliated with the Free Syrian Army.
With the takeover of Idlib, the Nusra Front further cements its hold on land it controls stretching from the Turkish border to central and southern Syria.
With the world's attention focused on the Islamic State, the Nusra Front has quietly consolidated its power in Syria in recent months, crushing moderate rebel groups that the West may try to work with while increasingly enforcing its own brutal version of Islamic law.
A Syrian opponent of Assad from Idlib who now lives in Turkey said he was overjoyed the city has been liberated but was not planning to return because he feared the hard-line Islamic groups that took over would start infighting.
"I am worried about what will follow," he said, adding there were also fears about retaliatory government airstrikes. He spoke on condition of anonymity, fearing retribution against family members still in Idlib.
The main Western-backed Syrian National Coalition opposition group said the liberation of Idlib is an "important victory on the road to the full liberation of Syrian soil from the Assad regime and its allies." However, it said more "decisive" assistance to Syrian rebels was needed for that to happen.
The Britain-based Syrian Observatory for Human Rights said rebel fighters seized control of Idlib in a push Friday evening and early Saturday after rapidly collapsing government forces withdrew.
The group said some fighting continued Saturday amid heavy artillery shelling from both sides.
The Local Coordination Committees, another opposition activist collective in Syria, also reported the "almost complete" capture of Idlib by rebels.
Meanwhile, U.S. military and intelligence agencies are doing background checks on the first 400 Syrians to be trained to combat Islamic State forces in their country, with a target date set as early as September for them to join the war, the Pentagon said Friday.
About 1,800 other Syrians have been identified as candidates for the program.
It was the first official word that the U.S.-led effort to equip and train thousands of Syrians to fight the Islamic State has begun, four months after Congress approved spending $500 million on the program.
More than 350 U.S. troops have arrived in Turkey and other nearby countries in preparation for the training, the Pentagon said.
"If all goes well, we expect they'll be finished with training in late summer or early fall," Army Col. Steve Warren, a Pentagon spokesman, said of the first group.
The United States expects 3,000 Syrians to have completed training by the end of the year and 5,000 to be finished by next April, Warren said.
Elsewhere on Saturday, U.N. Secretary-General Ban Ki-moon said he was angry and shamed by the failure of the world to stop Syria's civil war.
He promised to step up diplomatic efforts in comments at a summit of Arab leaders in the Red Sea resort city of Sharm el-Sheikh in Egypt.
More than 220,000 people have been killed in the conflict, which began with popular protests during the Arab Spring uprisings in March 2011 and turned into an insurgency after a brutal military crackdown.
Information for this article was contributed by Zeina Karam, Albert Aji and Hamza Hendawi of The Associated Press and by James Rosen of Tribune News Service.
A Section on 03/29/2015