At least 25 people have been killed in an explosion outside a polling station in the Pakistani city Quetta, officials say.
Five policemen and two children are among the dead and there are fears the death toll could rise as many of the wounded are in a critical condition.
More than 40 people are being treated in hospital.
Hashim Ghilzai, an administration official in Quetta, said: “(The bomber) was trying to enter the polling station. When police tried to stop him he blew himself up.”
No group immediately claimed responsibility for the explosion.
The attack came as tens of millions of Pakistanis headed to the polls to vote in an election that could have repercussions for the entire region.
If successful, the elections will mark only the second time a civilian government has handed power to another since the country’s independence in 1947.
The race to be the country’s next prime minister is tight, but most polls are predicting a narrow victory for the former Pakistan cricket captain Imran Khan.
The head of the centre-right Pakistan Tehreek-e-Insaf party is likely to have to form a coalition if he wants to govern though.
Quetta is the capital of Balochistan, Pakistan’s poorest province, which suffers from Islamist and separatist insurgencies.
It was hit by several bombings during the election campaign including Pakistan’s deadliest ever suicide attack earlier this month when a blast by Islamic State killed 153 people.
An attack in the province on Wednesday left one policeman dead and three wounded when a hand grenade was thrown at a polling station in the village of Koshk, in Khuzdar district.
The military has stationed more than 370,000 personnel across Pakistan to ensure security for the election, bolstered by an additional 450,000 police.