Karachi was gripped by panic on Thursday and parts of the throbbing metropolitan came to a virtual standstill after reports came regarding the murder of top Muttahida Qaumi Movement (MQM) leader Imran Farooq in London by an unidentified attacker.
Farooq was returning from an evening walk in the Mill Hill area of London on Thursday when he was attacked near the entrance of his house.
Media reports said knives were used in the attack and the head injuries he sustained proved fatal. Scotland Yard and the Pakistani High Commission in London have confirmed the death.
Meanwhile in Karachi, several eateries that usually remain open throughout the night were closed immediately soon after the news broke out.
Petrol pumps were closed and two vehicles were burnt by an angry mob, while there was no traffic to be seen in a few areas of the city.
MQM party leaders gathered at the residence of Imran Farooq's parents to offer their condolences.
Farooq had moved to London in 1992 after a crackdown was launched by Pakistan's military against the MQM.
He was serving as MQM convener and was considered the right-hand man of party chief Altaf Hussain.
Hussain's birthday was on Thursday, and Farooq was scheduled to address a large public gathering in Pakistan via telephone from London.
Speaking to the media, MQM deputy convener Farooq Sattar termed it as a great loss for the party and announced a 10-day mourning.
"All party affairs will remain suspended during this period while the birthday celebrations of party chief Altaf Hussain have also been cancelled," he said.
There were moving scenes outside Farooq's parents' house and the MQM headquarters, but there was no immediate confirmation of the funeral plans of the deceased.
"We will decide after consulting with the family," Sattar said.
"I have lost a personal friend and trustworthy colleague," MQM chief Altaf Hussain said from London in a sobbing voice.
He prayed for the departed soul and said, "the culprits would not be able to escape".
MQM has a political stronghold in Karachi and other urban areas in Sindh province.
The city has been witness to killings of political workers during the last couple of years and this was the second high-profile target of MQM after provincial legislator Raza Haider was killed last month.