Hundreds of demonstrators have held protests in London, after gunmen shot and killed a senior member of a leading Pakistani political party outside her home in the city of Karachi in southern Sindh province.
The Pakistan Tehreek-e-Insaf PTI's leader, former international cricket star Imran Khan, immediately blamed the killing of Zara Shahid Hussain on the Muttahida Quami Movement.
Mr Khan, who leads the Pakistan Tehreek-e-Insaf party, has blamed the death on the Muttahida Quami Movement's leader Altaf Hussain, who lives in the UK.
London's Metropolitan Police clarified it has not arrested anyone associated with a Pakistan political party following Imran Khan's comments that he held the British Government responsible for the killing of a senior politician:
The Pakistan Tehreek-e-Insaf PTI's leader, former international cricket star Imran Khan, immediately blamed the killing on the Muttahida Quami Movement.
The MQM has a stranglehold on politics in Pakistan's biggest city, Karachi.
"Her death has sent shockwaves across the rank and file of the party," Khan said in a statement. Police said that two gunmen shot Hussain dead outside her home in an upscale neighborhood of Karachi, he said.
"I hold (MQM leader) Altaf Hussain directly responsible for the murder as he openly threatened PTI workers and leaders through public broadcasts," he added in a tweet.
"I also hold the British government responsible as I had warned them about British citizen Altaf Hussain after his open threats."
Gunmen killed a senior female politician from a reformist party in Pakistan on Saturday night, the latest violent incident in a bloody election campaign and one that set off a war of words between two major opposition parties.
Around 150 people were killed in the run-up to national elections held last week, which handed a landslide victory to opposition leader Nawaz Sharif and his PML-N party.
It marked the first time an elected government replaced another one in a nation that has been run by military leaders for more than half its history.
Results from a handful of constituencies are still awaited amid accusations of vote-rigging.The shooting came hours ahead of re-polling in a key area beset by allegations of voting fraud.
It was not immediately clear who killed Zara Shahid Hussain, a senior member of the Pakistan Tehreek-e-Insaf party.
The PTI has promised to reduce endemic corruption in the nuclear-armed nation of 180 million people.