Saddiq Zaman Khattak, running for Parliament in next week's historic Pakistani election, was shot dead on Friday along with his three-year-old son after praying in a mosque in Karachi, police said.
It is the first time that a national assembly candidate has been killed in Pakistan's election campaign. Campaigning has been marred by Taliban threats and attacks, which have killed 62 people since April 11, according to an Agence France-Presse (AFP) tally.
The May 11 polls for the national and regional assemblies mark the first time that a civilian government completes a full-term and hands over to another at the ballot box, in a country that has been ruled by the military for half its life.
Saddiq Zaman Khattak was a businessperson and a candidate for the Awami National Party (ANP), the leading secular party in Pakistan's ethnic Pastun north-west. A party leader said he had received threats.
"He was returning from a mosque after saying his Friday prayers with his three-year-old son when gunmen on a motorbike opened fire. Both were killed," police spokesperson Imran Shaukat told AFP.
Senior ANP leader Bashir Jan confirmed the attack and the deaths.
Democratic elections un-Islamic
There was no immediate claim of responsibility, but the Taliban has directly threatened the ANP and the two other main parties in the outgoing government, branding the democratic elections un-Islamic.
Karachi, a city of 18-million people, contributes 42% of Pakistan's gross domestic product but is rife with politically and ethnically linked violence.
Friday's assassination brings to three the number of constituencies where the May 11 election will now be delayed because candidates have been killed.
A man standing for the secular Muttahida Qaumi Movement (MQM) in the Sindh provincial assembly, of which Karachi is the capital, was shot dead in the southern city of Hyderabad on April 11.
An independent candidate for the Baluchistan provincial assembly was also killed in the south-western town of Jhal Magsi on Tuesday.
Karachi has seen a string of attacks on the election campaign.
'Expose the real culprits'
Late on Thursday, a bomb wounded at least five people near an election office for MQM, the party that dominates Karachi.
Three bombs, two of which targeted MQM and the Pakistan People's Party, killed three people and wounded 49 others on Saturday.
In the capital Islamabad on Friday, Pakistan's main state prosecutor in the 2007 murder of former prime minister Benazir Bhutto and the 2008 Mumbai attacks, was shot dead en route to a court hearing on the Bhutto case, police said.
Chaudhry Zulfiqar was shot multiple times after gunmen intercepted his vehicle after he left home. His bodyguard was also wounded and a woman passer-by killed.
President Asif Ali Zardari, Bhutto's widower, condemned the killing and ordered a thorough investigation to "expose the real culprits involved in the murder", his office said.
Former military ruler Pervez Musharraf was this week placed under two-week house arrest over charges that he conspired to murder Bhutto.
Nobody has ever been convicted or jailed for Bhutto's assassination in a gun and suicide attack after a campaign rally in Rawalpindi on December 27 2007.
Musharraf's government blamed the killing on Pakistan's Taliban chief Baitullah Mehsud, who denied any involvement and was killed in a US drone attack in 2009.
In 2010 a UN report said Bhutto's death could have been prevented and accused Musharraf's government of failing to give her adequate protection.
Zulfiqar was also the main government prosecutor who indicted seven alleged conspirators in the 2008 Mumbai attacks, which killed 166 people and which were blamed on Pakistan's Islamist group Lashkar-e-Taiba. – AFP