Zara Shahid Hussain, 59, vice-president of the women's wing of PTI in the province of Sindh, was targeted by gunmen on a motorcycle outside her home in an upmarket part of Karachi.

A founding member of the PTI, Hussain was chief polling agent for the constituency where the PTI accused its rival Muttahida Qaumi Movement (MQM) of rigging last week's election.

Nobody has claimed the killing.

Khan blames MQM

Former cricket star Khan was swift to blame on the MQM, which represents the Urdu-speaking majority, and specifically its boss, Altaf Hussain, who lives in exile in London. He also said he holds the British government responsible.

"I hold Altaf Hussain directly responsible for the murder as he had openly threatened PTI workers and leaders through public broadcasts," Khan said on his Twitter feed, describing the killing as "a targeted act of terror".

"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," he said, adding that he was "shocked and deeply saddened by the brutal killing".

He himself is still in hospital recovering from a fall during his election campaign.

In a statement issued from London, Altaf Hussain condemned the murder and expressed his condolences.

British police are currently looking into a recent speech by Altaf Hussain in response to allegations that it was an incitement to political violence.

"Women have high stakes in the process of change" - discussion on the future of Pakistan

Point blank

Police said all three gunmen escaped after the attack.

The motive behind the shooting was unclear and there was no immediate claim of responsibility for the attack.

The killing came hours before voting was due to start at 43 polling stations in Karachi - the country's financial hub - in a partial re-run ordered due to allegations of rigging in last weekend's polls, which marked Pakistan's first democratic transition of power.

Partial re-vote Sunday

Tensions have been running high between PTI and the MQM, Karachi's dominant party, after Khan's party accused its rival of widespread vote-rigging. MQM denied the charge and announced a boycott of the re-run.

PTI and the right-wing Jamaat-e-Islami party have staged nationwide protests against the alleged irregularities.

Pakistan's election commission ordered the partial re-run due to allegations of ballot stuffing in a constituency known as NA-250 -- largely an affluent neighbourhood of the financial capital.

The re-vote does not affect the main results, though it appears that the PTI has now gained one seat in the disputed district. Final results are not yet in for all areas due to vote-rigging charges and some re-votes.

Election

The May 11 election saw some 50 million Pakistanis vote, with centre-right former prime minister Nawaz Sharif emerging the winner nearly 14 years after he was deposed in a coup.

The Taliban, who denounce democracy as un-Islamic, killed more than 150 people during the election campaign, including 24 on polling day.

(Voice of Russia, AFP)