The polling began at 8 am with around 4,500 cops deployed in the area to avert any untoward incident and continued uninterrupted till 5pm.
A fierce contest is expected between PTI, JUI-F and ANP for the National Assembly seat in Hangu.
Hangu District Police Officer Ikramullah said during a media talk that the security arrangements had been finalized by the Election Commission of Pakistan (ECP) to hold a peaceful and transparent by-poll.
He said the police, along with the Quick Response Force and Rapid Response Force personnel, would patrol across the constituency during the polling process, while the Frontier Reserve Police would remain on standby at the police lines to cope with any emergency.
Over 0.314 million people are exercising their right to vote and five candidates are contesting in the by-election on NA-33, the seat which fell vacant after the demise of PTI MNA Haji Khayal Zaman in February.
The candidates are Saeed Umar of Awami National Party (ANP), Obaidullah of JUI-F, Nadeem Khan of PTI and Atiq Ahmed and Muhammad Saeed, who are running as independent candidates.
A spokesperson of the ECP said 210 polling stations, including 55 for women only and 91 combined for both men and women, have been set up for the poll.
According to the official, 110 of these polling stations were declared sensitive while 77 had been declared highly sensitive.
Chief election commissioner appealed to voters to exercise their right to vote without any fear, saying that no interference in the polling process will be tolerated and immediate action will be taken against any violation.