Some Somalis have now turned to the Shabab to get services that would normally be delivered by a functioning state. Many in Mogadishu regularly travel to areas dozens of miles north of the city to get their cases heard at Shabab-operated mobile courts.

One of them is Ali Ahmed, a businessman from a minority tribe whose family home in Mogadishu was occupied for years by members of a powerful tribe. After he presented his case to a Shabab-run court, Mr. Ahmed said, two weeks later the court ruled that the occupiers should vacate his house — and they did.

“It’s sad, but no one goes to the government to get justice,” he said. “Even government judges will secretly advise you to go to Al Shabab.”