Heavy gunfire was heard in Pakistan's southern megacity Karachi on Saturday evening, AFP journalists said, following reports of an explosion.Armed service personnel cordoned off streets around the Mosamiat Chowrangi area of the city, the capital of Sindh province, as gunshots could be heard.The Sindh chief minister said he had "taken notice of the reported sound of an explosion and the alleged firing", adding he had called for a detailed report into the incident."Police should immediately reach the scene, determine the nature of the incident, and take all necessary measures," Syed Murad Ali Shah said in a statement.A statement from the Edhi Foundation, which provides emergency assistance in Pakistan, said at least two people were injured and taken to hospital.AFP journalists saw armed service personnel standing guard at closed roads near the scene.