Senior Pakistani politician Zahra Shahid Hussain was killed outside her home in Karachi Saturday, the BBC confirmed.
Hussain was the senior vice president of Pakistan's Movement for Justice party (PTI), led by former cricketer Imran Khan.
Her funeral was held at a mosque in Karachi Sunday afternoon.
Khan has blamed rival MQM party leader Altaf Hussain for Shahid Hussain's murder, which MQM continues to deny.
"I also hold the British government responsible as I had warned them about British citizen Altaf Hussain after his open threats to kill PTI workers," Khan tweeted Saturday evening, in reference to Altaf's self-imposed exile in London, where he has lived since 1991.
Pakistan's Dawn newspaper reported senior police official Nasir Aftab said the shooting was a result of an attempted robbery.
Aftab told the Express Tribune that Hussain’s daughter told police "two men on a bike pulled up and tried to snatch her purse as they were leaving their home."
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According to her daughter, "when [Hussain] resisted they shot her" twice in the head.
However, the reports raise questions about whether it was a politically motivated murder made to look like a robbery.
The PTI leader also tweeted that:
Hussain's death comes just hours before the polls opened for voting in a partial re-run of last week's general election which has been plagued by allegations of vote rigging.
Khan urged voters to make it out to the polls in spite of the violence:
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Sources reported Hussain was rushed to the National Medical Center but died before arriving. A full autopsy is currently underway and is expected to be released within the next 24 hours, BBC News reported.
"She was an asset of the party...and I believe the Sindh [provincial] government should investigate this murder, look for the killers and get them sentenced," Arif Alvi, the PTI's candidate for the NA-250 constituency in Karachi, told Al Jazeera. "But, unfortunately, over the last five years, nobody has ever been arrested for [political] killings or tried in a court of law."
Pakistan's elections last weekend — the country's first democratic handover of power since 1947— was marked by violence that left at least 150 dead.