|Farooq claimed asylum in Britain 11 years ago after being accused of murder and other crimes [File: AFP]
Karachi, Pakistan's biggest city, has been effectively shut down after a senior politician of the dominant Muttahida Qaumi Movement (MQM) was stabbed to death in London.
Gas stations, schools and markets in Karachi were all closed on Friday and public transport was not running as news of the killing of Imran Farooq, a founding member of the MQM party, spread.
Osama Bin Javaid, a senior editor at Pakistan's Dawn News, told Al Jazeera that Karachi was in "sombre mood".
"It is a city in shock and fear right now ... there is very little traffic on the streets and the city wears a deserted look," he said.
"There have been scattered pockets of violence in several parts of the city. Shops have been burned and vehicles set alight ... It is very much waiting and bracing itself for if there will be a backlash."
It is feared that the killing could trigger more ethnic and political violence in Karachi. Revenge attacks and random acts of arson often follow high-profile murders in the southern Pakistan city.
"If this murder had happened in Karachi it would have triggered a severe reaction. Now, there is a tense calm prevailing over the city," Al Jazeera's Kamal Hyder reported from Islamabad, the capital of Pakistan.
"We cannot say that this is a political murder because it is still under investigation"
MQM party member
"There were serious differences within the MQM, a party with a history of infighting. It is also locked in a conflict over control over the city of Karachi."
Farooq was found in the north of the UK capital on Thursday with multiple stab wounds and head injuries, however it was not clear if it was politically motivated.
Alan Fisher, Al Jazeera's correspondent in London, said: The street where it happened is still closed off as police carry out their checks, talk to neighbours.
"Neighbours reported hearing a disturbance and Imran Farooq's body was found with head injuries and several stab wounds to his body and also his head.
"At this stage [police] are not ruling out any possible motives, including a political background to this killing."
"At the moment the whole party is very sad and deeply touched. It is the biggest incident in the history of MQM," Khush-Bakht Shujat, a member of Pakistan's parliament for the MQM party, told Al Jazeera.
Shujat did not want to speculate who could be responsible for the killing.
"It is too early to say anything. We cannot say that this is a political murder because it is still under investigation."
The MQM is a member of Pakistan's ruling coalition and has a strong anti-Taliban stance.
The government has blamed the Taliban and the banned the Sunni group Sipah-e-Sahaba Pakistan (SSP) for the killing of the former parliamentarian.
"We are confident that the culprit will be arrested and will be given exemplary punishment," Farooq Sattar, a senior member of the MQM and a minister in the government of president Asif Ali Zardari, told reporters in Karachi.
Sattar refused to speculate on the motives behind the killing, saying they were awaiting results of British investigations.
Farooq, inactive in politics for about two years, claimed asylum in Britain 11 years ago after more than seven years on the run from Pakistani police who accused him of involvement in murder and other serious crimes.
|Farooq was found stabbed near his home in north London[Reuters]
He had denied the charges.
Farooq was one of several senior members of the MQM who have taken refuge in London. The party's senior leader, Altaf Hussain, has lived in self-exile in the British capital since 1992.
The party represents the descendants of Urdu-speaking migrants from India who settled in Pakistan after the partition of the subcontinent at the end of British rule in 1947.
Up to 100 people were killed and hundreds wounded in several days of clashes in Karachi last month after MQM member Raza Haider, who was a Shia Muslim, was gunned down along with his bodyguard while attending a funeral.
Karachi has seen hundreds of targeted killings this year.
MQM party workers were involved in bloody factional clashes and battles with the security forces in Karachi in the 1990s.
Source: Al Jazeera and agencies