ominous

threatening or foreshadowing evil or tragic developments

Of or pertaining to an omen or to omens; being or exhibiting an omen; significant; portentous; -- formerly used both in a favorable and unfavorable sense; now chiefly in the latter; foreboding or foreshowing evil; inauspicious; as, an ominous dread.

Latin 'auspicium' meaning omen

“He decided that it meant something, and something ominous--but what?”

— George Meredith, Complete Project Gutenberg Works of George Meredith

Daisuke stood near Dhaka's old clock tower, chuckling at the ominous shadow it cast, stretching like a bony finger over the marketplace. "Watch out," he joked to a group of children, "the shadow's planning mischief!" They giggled, but one little girl clung tighter to her mother’s skirt.

Owen walked along the narrow streets of Lagos Island as the sun began to set, casting long shadows. Suddenly, a heavy silence fell over the market; vendors paused in their calls, and even the distant drumming ceased as an ancient, gnarled tree loomed ominously at the end of the alley, its branches stretching like bony fingers.

“The relief was immediately hidden by tarpaulins to conceal the accident and avoid any undesired ominous interpretations.”