Imran was barred from contesting the election and his popular Pakistan Tehreek-e-Insaf (PTI) faced a pre-poll widespread crackdown.
PTI candidates are participating in the election but have been denied the use of the party's cricket bat electoral symbol, a huge disadvantage in facing their rivals from two other major parties -- the Pakistan People's Party (PPP) of former foreign minister Bilawal Bhutto Zardari, and the Pakistan Muslim League-Nawaz (PML-N) of former prime minister Nawaz Sharif.
Pakistani celebrities encouraged people to turn out in large numbers to vote.
"Voting is not only our right -- it is our power!" said cricketer Shaheen Afridi, urging people to go out and vote for a "better Pakistan."
"No matter what you feel or who you want to vote for, it's important that we exercise our fundamental right to vote. See you all at the polls," actress Mahira Khan said.
President Arif Alvi told the nation of 241 million people that electing their representatives was "your Islamic, constitutional and civic responsibility".
"We as a family reached our polling station, stood in line and have voted and urge all of you to come out and exercise your right. Pakistan needs your opinion as never before," he said in a social media post.
More than 90,500 polling stations were set up to allow 128.5 million registered voters to cast their votes in the country's 12th general election.
They will elect 266 members of the National Assembly as well as decide the fate of Punjab, Sindh, Balochistan and Khyber Pakhtunkhwa provincial assembly candidates.
The National Assembly has a total of 336 seats, with 60 seats reserved for women and 10 for non-Muslims.
-- BERNAMA
