The main contests are expected to be between candidates backed by Khan, whose Pakistan Tehreek-e-Insaf (PTI) party won the last national election, and the Pakistan Muslim League of three-time premier Nawaz Sharif, who is considered the front-runner.

Unofficial first results in the election are expected a few hours after voting closes at 5 p.m. (1200 GMT) and a clearer picture is likely to emerge early on Friday (February 9).