The explosion took place on the outskirts of Quetta, capital of Baluchistan province. The cause of the explosion is unknown, said the police superintendent of the city, Quetta, Naseeb Ullah.
Shopkeeper Akber Khan, who witnessed the attack, said he had already cast his vote at a nearby polling station and had returned to his shop. He stepped outside again and had "barely taken a step or two steps" as the explosion started.
"We fell to the ground, most people started running, and after 10 minutes of chaos, we started picking up the injured and carrying them in private vehicles because the ambulances had not arrived yet. "
The IS has taken responsibility for the attack. CNN can not independently verify this claim.
In Khyber Pakhtunkhwa, one person was killed and three injured in a battle at a polling station between supporters of Imran Khan's Pakistan Tehreek-e-Insaf (PTI) and the province's Awami National Party.
Khan condemned the Quetta explosion He said in a tweet that he was "saddened by the loss of innocent lives" and added that "enemies of (Pakistan) are trying to disrupt our democratic process … Pakistanis need that Defeating the terrorists' design by entering into force voting. "
The election has included the party of cricket star Khan Stagger brought a fiercely competitive race against that of detained ex-prime minister Nawaz Sharif.
Shahbaz Sharif, who replaced his brother as a candidate for their party, said in a tweet, "Heartbroken, to learn of the martyrdom of innocent people, including police officers … My deep condolences to the bereaved."
Police and military were in the election in force stations across the country, with security guards flying surveillance drones in the troubled northwestern city of Peshawar. In the big cities of Karachi, Quetta and Peshawar, long lines of voters were queuing up.
Army officers said more than 370,000 soldiers were deployed to ensure a "fair and free" election, with police estimated the entire security force at 800,000.
"Air of Fear" as cast votes
Speaking to CNN in Peshawar, 36-year-old Sumera Khanum said the Wednesday's election was only the third time in her life that she had cast her vote.
"There's a touch of fear, but we have to get out and vote," she said. "Women should vote with men in large numbers."
The graduate of the university, Amina Shams, 26, who voted for the first time, said, "We want to bring change to the youth."
But she added that there was a "sense of fear in Peshawar … when I left the house this morning, I was scared."
8 am local time (11 am ET): Polls open
6 pm (9 pm ET): Polls close (could be at 7 pm / Extended by 10 o'clock if there are large turnouts or delays in voting)
8-9 o'clock (11-12 o'clock) ET): Pakistan's Electoral Commission begins to announce regional results
From 11 pm (2:00 pm ET): General results should get in shape, candidates may start or terminate
The headlines of the newspapers on Wednesday were dominated by the crucial election, one being of which was described as "sharp-edged". Many also noted the strong presence of security as voters went to the polls.
Nearly 106 million people are registered to elect members of the lower house of parliament and four provincial assemblies.
This week's election is only the second time in Pakistan's 71-year history that the country has undergone a democratic transition achievement.
The Human Rights Commission of Pakistan (HRCP) has expressed "serious reservations about the extraordinary powers of the security forces" and called the election "the dirtiest" in the country's history.
The military has governed Pakistan for most of its history directly or indirectly control over defense and foreign policy as well as its own business empire.
Khan has repeatedly rejected the claim that he is supported by the military and condemned the harassment of electoral candidates.
The former Pakistani cricket captain said he voted and told reporters, "I'm an athlete, I will not declare victory until the last shell has rolled."
With Sharif's incumbent Pakistan Muslim League-Nawaz (PML-N), who is still on the back foot after his imprisonment, puts the Choosing a real opportunity for Khan's center-right PTI to break into the two party system that has traditionally dominated national politics.
The end result, however, may be forgotten. The coalition negotiations with the formerly dominant Pakistani People's Party (PPP) under the leadership of 29-year-old Bilawal Bhutto Zardari, the son of former President Asif Ali Zardari, are therefore pending and Prime Minister Benazir Bhutto.
In Pakistan, there are a multitude of smaller parties that could gain new meaning when Khan or another candidate has to rely on them to form a coalition government. These marginalized groups include some far-right Islamist parties, some of whom sympathize with militant groups.
"It has been a while since Pakistan's political environment has been so tense and polarized, so I imagine every coalition will be divided and split," said Michael Kugelman, a South Asia expert at the Wilson Center in the US.
Khan built on his sporting fame and the success of the PTI as a regional party to act as a change candidate, attracting religious conservatives and drilling on Pakistan's endemic corruption – a task facilitated by Sharif's conviction.
When the elections started on Wednesday, Khan supporters were optimistic that, if elected, his slogan of building a "new Pakistan" would bear fruit.
"I just voted for PTI," said Amna Gardar in Lahore, the capital of Punjab. "If you want to be part of this change, please come, please vote."
All eyes will be on whether Shahbaz Sharif can capture the PML-N in Pankschab, Pakistan's most populous and wealthiest province. It will be extremely difficult for Khan to take power without winning Punjab. The analysts agreed that Sharif's detention would trigger a sympathy vote.
When the first voters flocked to the polling stations, Shahbaz tweeted that he had cast his vote and urged his compatriots to vote.
You have all come to vote for Pakistan's progress and prosperity, "he said," May this election be a source of peace and stability for the nation! "
In Balochistan voters defied elections despite the fact that "I'm voting for the Pakistan Peoples Party," said Syed Izatullah, a young voter standing in front of a polling station in Quetta, adding that Bilawal Bhutto could liberate Pakistan from its difficulties.
"I agree with Muttahida Majlas e Amal (a religious alliance), "said Habibullah Khan, the black-bearded man.