Senior police official Javed Odho said that they had received complaints of armed men taking to the streets and resorting to firing which led to panic and closure of businesses since last night.
"Unidentified men contacted shop owners by cell phones and threatened them to close down their shops," Odho confirmed.
As a result of the unannounced strike most public events scheduled for the day in the city were postponed including the annual elections of the Karachi Bar Association and public transport also remained scarce.
Panic and fear had gripped the city after there were reports of armed men in many areas asking businesses and shops to shut down while aerial firing was also reported from some places.
No political party or group has so far claimed responsibility for the shutdown which came hours after a larger bench of the Supreme Court headed by the Chief Justice issued a contempt of court notice against Altaf Hussain chief of the Mutthaida Qaumi Movement the single largest party in the city.
Television channels reported that businesses and shops were also closed in areas of Hyderabad, Mirpurkhas and Sukkur where the MQM has a vote bank among the Urdu speaking migrants from India.
