A senior member of Imran Khan's Movement for Justice party (PTI) was shot dead on Saturday outside the gates of her home in Karachi, Pakistan, hours before several re-elections were scheduled to take place in the country on Sunday.
Zohra Hussain, 59, was a senior vice-president of the PTI in the southern Sindh province. She was shot by one of three gunmen who approached her by motorcycle outside her residence.
Motivations for the killing were still unknown Sunday.
However, while police claimed it was the result of an armed robbery, Khan, known for his anti-corruption, anti- U.S. drone campaign, said he was certain it was the work of the city's MQM party.
"I am shocked and deeply saddened by the brutal killing of Zara Shahid Hussain, Zara apa to us, in Karachi tonite. A targeted act of terror!" [sic] Khan tweeted.
"I hold [MQM leader] Altaf Hussain directly responsible for the murder as he had openly threatened PTI workers and leaders through public broadcasts."
"I also hold the British Govt responsible as I had warned them abt Br citizen Altaf Hussain after his open threats to kill PTI workers."
Charges of vote rigging surged in Pakistan last week immediately after it was announced that former Prime Minister and rich industrialist Nawaz Sharif overwhelmingly defeated challenger Imran Khan—who had built a massive movement behind his PTI.
Sharif, who is a conservative and advocates free-market economics, is likely to pursue increased privatization and deregulation.
Hussain's murder happened on the eve of the highly contested partial vote rerun for local officials in the Karachi district—where the PTI says many of the polls were rigged.
An upmarket constituency of Pakistan's violence-plagued city of Karachi voted again under tight security on Sunday, a day after gunmen killed a senior politician from a reformist party in the district and a week after general elections.
It was not immediately clear who killed Zara Shahid Hussain, a leading member of the Pakistan Tehrik-i-Insaf (PTI) party of former cricket star Imran Khan.
Imran blamed the killing on the Muttahida Quami Movement (MQM) party, which has a stranglehold on the city. MQM leaders denied responsibility, condemned the killing and demanded a retraction from Imran.
The attack in the upscale Defence area, the family neighborhood of assassinated former prime minister Benazir Bhutto, capped a bloody election campaign in which around 150 people were killed nationwide.
Last Saturday's elections handed a landslide victory to opposition leader Nawaz Sharif and his Pakistan Muslim League-Nawaz (PML-N).
But results from a handful of constituencies across the country are still uncertain amid accusations of vote-rigging. There is re-polling in a few others where security issues prevented voting.
Last week's election gave the MQM 18 of 19 national assembly seats in Karachi, Pakistan's biggest city. The constituency, known blandly as NA-250, where Sunday's re-poll is taking place is thought to be a stronghold of the PTI.
The re-vote took place at 43 of 180 polling stations. The MQM, which wanted re-polling of the whole constituency, boycotted the vote.
Whatever the result, Sharif's national landslide win is assured. But as Pakistan's financial center, Karachi generates around half of government revenues and stability in the city is key to stability of the whole country.
For the first time, each ballot box was guarded by a ranger and a soldier inside and outside the booths to ensure security and no violence had been reported by early afternoon.