Nawaz Sharif is set to become prime minister of Pakistan for the third time as the 342-member National Assembly started its session Wednesday to elect a new prime minister.
Amin Faheem of the Pakistan People's Party and Javed Hashmi of the Pakistan Tehreek-e-Insaf are also standing for the office of prime minister.
"Let the bells ring for five minutes calling the members of the national assembly to reach the hall," speaker Ayaz Sadiq said at the start of the election process.
The election is to take place by division.
Supporters of each candidate have assembled in three lobbies, with staff members of the National Assembly counting the supporters in each lobby.
The National Assembly speaker will later Wednesday be informed about the number of votes secured by each candidate.
Sharif of the Pakistan Muslim League (N) was prime minister from November 1990 -- May 1993 and February 1997 -- October 1999, but wasn't able to complete either term.
In 1993 he was sacked over corruption charges by President Ghulam Ishaq and in October 1999 Sharif's chief of Army Staff, Gen. Pervez Musharraf, overthrew the government in a bloodless coup.