A train in Pakistan smashed into derailed carriages of another train on Monday, killing at least 36 people, government officials said, in the latest accident to highlight the perilous state of a more-than-165-year-old railway system.

The death toll was likely to rise as rescuers struggled to reach people trapped in several mangled compartments strewn across the tracks in the southern province of Sindh.

A Pakistan Railways spokesperson said at least 33 bodies had been taken to hospitals, among them two railway officials. More than 100 people...