Investigators said the killing of Zahra Shahid Hussain, carried out by two men on motorbikes, was a robbery gone wrong, The (London) Guardian reported. But Khan, the cricket star turned politician, suggested the United National Movement or MQM party, which dominates politics in Pakistan's largest city, and the British government were behind the shooting.
Hussain, 60, was the senior vice president of Khan's party, known by its Pakistani initials, PTI. Her death occurred on the eve of a rerun of last Saturday's election in some districts.
On Twitter, Khan said Hussain was the victim of "a targeted act of terror." He said he had warned the British government about a British national who had made threats against his party.
MQM leaders condemned the crime while emphasizing police had described it as non-political.
"As per Zahra Shahid Hussain's daughter and driver, the eyewitnesses, it was a street-crime related murder. She got killed resisting a robbery," the party said on Facebook.
The Pakistan Muslim League-N, headed by former Prime Minister Nawaz Sharif, appears to have won the largest number of seats in the general election. On Saturday, the party was involved in coalition talks with the Jamiat Ulema-i-Islam-Fazl or Association of Islamic Clergy.
The campaign and election were marred by violence with more than 20 political killings last weekend.