A blast targeting a police van killed more than 20 people in Pakistan's north western city of Quetta on Wednesday polling day.
The blast happened near a polling station, but it was unclear if voting had been disrupted.
"Over 20 bodies and 28 injured have been shifted to civil hospitals," Dr Waseem Baig, a spokesman for a Quetta hospital, told Reuters.
Television images showed a charred police vehicle, cordoned off by security officials.Samaa TV, which put the death toll at 20, said a "suicide attacker" was responsible for the attack. Rival Geo TV said 22 people had been killed.
Geo TV, quoting sources, reported that Zainab, the daughter-in-law of PML-N's prime ministerial candidate, had to return without exercising her franchise after she found her name missing from the voter list.
Nearly 106 million registered voters are casting their ballot to elect a new government in Pakistan, where a prime minister has never been able to complete his or her five-year term.
This is the second time in the country's 70-year history that the power is transferring from one civilian government to another. Yet, the whole election process has remained impaired.
As many as 122 parties have fielded candidates, many of who belong to extremist organisations.
26/11 attack mastermind Hafiz Saeed was seen ‘casting his vote’ during Pakistan’s 11th general elections in Lahore on Wednesday. The globally-designated terrorist, who carries a $10-million bounty on his head, is not contesting the polls.
Saeed's son and his son-in-law are among 265 candidates fielded by the Jamaat-ud -Dawah for national and provincial assembly seats across Pakistan in the July 25 general election, with the banned group's political wing vowing to make the country a "citadel of Islam."
Meanwhile, a large number of women are coming out in Peshawar to cast their votes, reported The Dawn.
The key parties, PML-N, Pakistan Tehreek-e-Insaf and Pakistan's Peoples Party, have promised employment, houses and social welfare for the country's 200 million people.