NAIROBI, Kenya—Kenyan police late Sunday struck to end a two-day terrorist attack at an upscale mall after the death toll rose to 68, with some 40 people believed trapped inside the complex while armed militants remained at large.

But the terrorist siege of an upscale Nairobi shopping mall pushed into a third day Monday morning, with a round of shooting sounding after dawn as helicopters circled overhead.

"I...