MOGADISHU, Somalia — An explosives-laden truck blew up at a busy intersection in the Somali capital on Saturday and killed at least 79 people, the latest sign of resurgent militant activity in a country plagued by an enduring strain of violent extremism.

A bus carrying university students to their campus was struck by the blast, which left the streets littered with bodies and the mangled frames of vehicles. The attack, which the government said also injured 149 people, was the worst in Somalia in more than two years.

There was no immediate claim of responsibility, but suspicion immediately fell on the Shabab, a terrorist group linked to Al Qaeda which controls large parts of the country and raises considerable funds through local taxation and extortion. Despite intensified American airstrikes and a long-running African Union offensive, the group has carried out deadly attacks not only in Somalia but also in neighboring Kenya and Uganda.