KABUL, Afghanistan >> As cafes, restaurants, and performance centers in Kabul came under attack one after another in recent years, the campus of the American University of Afghanistan remained a rare oasis for some of the country’s brightest young men and women.

Beyond providing a quality education, the school offered a glimpse of a carefree life away from the unpredictable violence that afflicted the rest of the capital. Behind layers of security, students could join a basketball game at the gym, compete in debate tournaments or even just have an uninterrupted conversation over coffee.

That sense of freedom, too, was violated last night.

Men with Kalashnikov rifles and grenades first gunned down a guard at the adjoining school for the blind. One drove a car packed with explosives into the American University’s walls, blowing a gap through it. Two more militants dashed onto campus, where hundreds of students were taking evening classes. The attackers methodically stalked the men and women trapped inside, fighting off the Afghan security forces for nearly 10 hours in a terrifying overnight siege.

On Thursday morning, at least 13 lay dead: seven students, three policemen, two university guards and the night guard at the neighboring school for the blind. Abdul Baseer Mujahid, a spokesman for the Kabul police, said that more than 30 others were hurt in the attack; another estimate, from the Health Ministry, said 16 had been killed and 53 wounded.

The attack was unmistakably a blow to young Afghans who had chosen to defy the migrant exodus away from the country’s war and instead pursue their dreams in the difficult circumstances at home.

Among the dead was Naqib Ahmad Khpulwak, a young lecturer in the university’s law department, who had recently completed a master’s degree in the United States through the Fulbright program and had returned to Afghanistan to teach. He soon expected to start a doctorate program in Britain.

“Your master’s degree is still lying in my pile of papers — you told me to get it stamped and approved,” one of his friends in the United States, Ayub Khawreen, wrote in a Facebook post. “My mouth be broken that I encouraged you to return home. But you wouldn’t listen to me anyway — you were boiling in your love for the country, and at the end you burned in that.”

From its start in 2006, the American University was a draw for the sons and daughters of prominent Afghan families. But many students of more humble backgrounds had won scholarships, and they were counted among the school’s most promising.

Sami Sarwari had been a student of the successful Afghan National Institute of Music, where his skills with the dilruba, a folk instrument, had made him part of an orchestra that traveled the United States and performed at the Kennedy Center.

After a 2014 attack at a performance center in Kabul where they were giving a concert, he quit music, according to his friend Shabeer Kabuli. This fall, Sarwari won a scholarship to the American University.

He was killed on his second day of classes. His last Facebook post, on Tuesday, had the American University tagged as its location. “I’m in,” he wrote. “Looking forward to a beautiful and bright future.”

“He had wished to support his family and be with them like a mountain,” said Ahmad Sarmast, the founder and director of the Afghanistan National Institute of Music, who taught Sarwari for six years and was among the wounded in the 2014 concert attack. “His family is so poor, and her mother tried to support her children to achieve their goals.”

On Thursday, President Ashraf Ghani condemned the attack as a barbaric act of enmity against progress. Out of safety concerns, the university remained closed.

All three of the attackers were killed, their affiliation still unannounced by Thursday evening. But another statement from Ghani’s office suggested that suspicion had fallen on the Haqqani wing of the Taliban, or some other Pakistan-based faction. Ghani called the Pakistani army chief, Gen. Raheel Sharif, and “asked for serious and practical measures against the terrorists organizing the attack,” the statement said.

Through the night, family members of the people trapped on campus gathered outside a security cordon, hoping for news. Some students inside took to social media to ask for help, but they later fell silent — many of them desperate to avoid alerting the gunmen to their hiding places.

Members of the Afghan special forces cut off the area’s electricity and began evacuating hundreds of students, moving slowly in an attempt to avoid civilian casualties, said Sediq Sediqqi, a spokesman for the Interior Ministry.

Security officials said both of the infiltrating gunmen entered the Bayat classroom building just after 7 p.m., when about 160 students were in class in the building. One of the militants had stationed himself near the stairs on the first floor, while the second had moved up to target the classrooms on the second floor. Most of the student casualties were caused by the first militant, who shot those trying to flee.

The militant on the first floor was killed around 1:30 a.m., officials said, while the gunman on the second floor resisted another two hours — lobbing grenades at Special Forces troops trying to reach him. The siege was declared over shortly before 5 a.m. Thursday.

Some of the people who had been trapped inside the university described a 10-hour ordeal, much of it spent waiting for death in complete darkness. They hid in gym lockers, or under classroom desks. Some jumped from upper floors, breaking their legs, while others managed to scale the walls of the compound.

Abdullah Frotan, a student who was trapped until the very end of the siege, said he had been in a third-floor classroom when the initial explosion occurred. About 10 students in his class tried to make it to the first floor to escape, but the gunmen were already inside the building, so they rushed back to the third floor and tried to hide in a classroom.

“We were lying like dead bodies on the ground in the rear of the class, and we put all the chairs in front of us, and we hid behind the chairs,” Frotan said.

Two of his classmates were wounded, one in the back and one in the leg, Frotan said. They held their hands over their mouths to stifle cries of pain that could alert the attackers.

“One of our classmates did not come back with us to the third floor. He was killed; we learned this later,” Frotan said.

Muhammad Daud, 26, an economics student, said he had recited his final prayers hiding under the tables on a third-floor classroom. The attacker fired a few rounds in the dark, and then moved on to the next room.

Daud agonized over whether to try to jump out a window. The gunman’s sudden return to the classroom made the decision easier. “When he started firing, I jumped and didn’t think what would happen,” he said.

Alnaz Jamal, an 18-year-old scholarship student who was starting her first week of college after years of displacement in Pakistan, did not make it.

Jamal, whom her family called Alina, had been attending a lecture on the second floor, and she was among those who jumped, said Omaid Sharifi, a cousin. When the family finally found her body at a morgue this morning, they saw she had also suffered bullet wounds.

Her father, a street vendor, was in Pakistan to get Jamal’s high school transcript as well as new clothes more appropriate for her university journey.

“Her mother faints every 15 minutes,” Sharifi said.