The blaze was the latest in a string of dramatic fires that have consumed the facades of skyscrapers in the United Arab Emirates in recent years, posing a challenge for firefighters and raising concerns about fire safety in the rapidly developing Gulf nation.
There were no immediate reports of casualties from Thursday's fire. The Sharjah civil defense directorate, whose fire crews were battling the blaze, had no immediate comment.
Sharjah resident Shane Jansen told The Associated Press he saw an apartment on one of the lower floors engulfed in flames. He said it appeared that the fire spread upward from there as gusts of wind fanned the flames.
"It looks like it crawled up the building," he said. "You see the fire calms down a bit, and then when the wind starts gushing up it starts rising up."
The densely populated city of Sharjah sits immediately adjacent to Dubai, the Mideast's booming commercial hub. It is home to hundreds of thousands of expatriate families and migrant workers, many of whom commute daily south into Dubai.
Fires have affected several skyscrapers in the Emirates, including a similar blaze in February that spread along the external cladding of Dubai's 86-story Torch tower, one of the world's tallest residential buildings. There were no serious casualties in that fire.