Isis has claimed responsibility for a deadly bomb attack near a polling station in Quetta, Pakistan, on the day of the country's general election.

Officials say the death toll has risen to at least 32, with scores more wounded. Isis claimed in its Amaq news agency that the attack was carried out by a suicide bomber, but did not provide further detail or evidence for its claim.

A witness told The Independent it looked like the attack targeted a police van, as the incident underscored the threats to democracy in a country where terror attacks have diminished but not disappeared entirely in recent years.

"The explosion occurred near a school where polling was taking place," witness Majeed Akbar said. "There was a cloud of smoke after the blast, it filled the sky and then after that I saw a pool of blood, dead bodies and others injured."

Another witness, Abdul Haleem, was queueing up to cast his own ballot when he said he saw a motorcycle drive straight into a crowd of voters. Mr Haleem's uncle was killed in the blast that followed, he said.

"There was a deafening bang followed by thick cloud of smoke and dust and so much crying from the wounded people."

Authorities have yet to comment on the nature of the blast. A spokesman for Quetta hospital, Waseem Baig, said 15 dead bodies were brought in to his hospital alone and 33 injured were under treatment there, some in a serious condition.

Pakistan general election: vote turns violent after suicide bombing Show all 22 1 /22 Pakistan general election: vote turns violent after suicide bombing Pakistan general election: vote turns violent after suicide bombing Pakistani security personnel gather at the site of a suicide attack near a polling station in Quetta AFP/Getty Images Pakistan general election: vote turns violent after suicide bombing A man who was injured in a suspected suicide bomb attack outside a polling station, receives medical treatment at a hospital EPA Pakistan general election: vote turns violent after suicide bombing Polling stations in Pakistan opened for the general election, for around 105 million constituents AFP/Getty Images Pakistan general election: vote turns violent after suicide bombing Pakistani politician Imran Khan, center, chief of Pakistan Tehreek-e-Insaf party, casts his vote EPA Pakistan general election: vote turns violent after suicide bombing Pakistani security officials inspect the scene of a suspected bomb blast outside a polling station, in Larkana EPA Pakistan general election: vote turns violent after suicide bombing A Pakistani woman and her son react after her husband was injured in a suicide attack AFP/Getty Images Pakistan general election: vote turns violent after suicide bombing Voters will have to choose from 11,000 candidates to elect 272 members of the Parliament for the next term REUTERS Pakistan general election: vote turns violent after suicide bombing Cricket star-turned-politician Imran Khan, chairman of Pakistan Tehreek-e-Insaf (PTI), speaks to members of media after casting his vote at a polling station during the general election in Islamabad REUTERS Pakistan general election: vote turns violent after suicide bombing Bilawal Butto Zardari, chairman of Pakistan People Party visits a hospital in Larkana to meet people who were harmed in a blast outside a polling station EPA Pakistan general election: vote turns violent after suicide bombing An election official marks a voters thumb before casting her vote AFP/Getty Images Pakistan general election: vote turns violent after suicide bombing At least 25 people were killed and 30 injured in the incident EPA Pakistan general election: vote turns violent after suicide bombing A polling officer shows empty ballot boxes prior to sealing them, at a polling station, in Peshawar EPA Pakistan general election: vote turns violent after suicide bombing People stand in a line as they wait for a polling station to open in Rawalpindi REUTERS Pakistan general election: vote turns violent after suicide bombing A man who was injured in a suspected bomb blast outside a polling station, receives medical treatment at a hospital in Larkana EPA Pakistan general election: vote turns violent after suicide bombing These elections are the second in Pakistan's history in which a government was able to complete its term to make way for another government after being ruled by military dictators for half of the 71 years of its existence since its founding in 1947 REUTERS Pakistan general election: vote turns violent after suicide bombing A rickshaw carries an electoral flag, as it rides past the mausoleum of Mohammad Ali Jinnah, early morning in Karachi REUTERS Pakistan general election: vote turns violent after suicide bombing Pakistani security officials inspect the scene of a suspected suicide bomb attack outside a polling station during general elections in Quetta EPA Pakistan general election: vote turns violent after suicide bombing A Pakistani soldier checks a voters information AFP/Getty Images Pakistan general election: vote turns violent after suicide bombing An man walks past a wall with electoral posters in Karachi REUTERS Pakistan general election: vote turns violent after suicide bombing A woman shows her thumb marked with indelible ink after she cast her ballot EPA Pakistan general election: vote turns violent after suicide bombing Shahbaz Sharif, second left, President of Pakistan Muslim League Nawaz party which concluded its mandate recently, lines up to cast his ballot EPA Pakistan general election: vote turns violent after suicide bombing Pakistani voters stamp their ballots at a polling station in Rawalpindi AFP/Getty Images

​Jaffer Kakar, a doctor, said two children and five policemen were among the dead.

Quetta, where the bombing took place, is the capital of Baluchistan province, which saw the worst of the pre-election violence.

Earlier this month, a suicide bomber killed 149 people at an election rally in the town of Mastung, also in Baluchistan province. The attack was claimed by Isis militants.

About 371,000 soldiers had been stationed at polling stations across the country to prevent attacks, nearly five times the number deployed at the last election in 2013.

Citing security concerns, the election commission announced that internet and mobile phone services in several districts in Baluchistan were suspended.

Election commission secretary Babar Yaqub told reporters that threats against polling stations, staff and even candidates have been received.

Hours earlier, militants lobbed grenades and opened fire at a military convoy escorting election staff and voting material in Baluchistan's district of Turbat, killing four troops.

Also on Wednesday, police said a shooting between supporters of two opposing political parties killed one person and wounded two in a village near the north-western city of Swabi.

Counting has now begun in the election which was seen as narrowly led in opinion polls by Imran Khan's PTI party, but otherwise too close to call.

Analysts see it as likely that PTI will be run close for the lead by the PML-N party of jailed former premier Nawaz Sharif. There is a good chance neither will take an absolute majority, opening the door to coalition talks and a kingmaker role for the PPP party, led by the son of former leader Benazir Bhutto.

Results are not expected until around 2am on Thursday morning (10pm Wednesday BST).