KARACHI - At least four MQM workers were killed and 42 others wounded in a high-intensity blast outside Jinnah Ground in the precincts of Azizabad police on Tuesday.According to details, the blast took place when the participants of a large gathering organised by Muttahida Quami Movement (MQM) started boarding the buses parked at Shahrah-e-Pakistan after the congregation.DIG Asif Ejaz Sheikh told newsmen that the explosive device fixed in a motorbike exploded near the buses arranged for the MQM workers. He said investigation was in progress. Immediately after the explosion, rescuers and law enforcers rushed to the crime scene and shifted the victims to Abbasi Shaheed Hospital for treatment. Those killed in the blast were Talib Hussain, Tayyab, Rehanullah Khan and Ashiq while several injured were in critical condition. The blast which created panic in the surrounding areas also damaged a number of cars and motorbikes. Hundreds of participants of the MQM gathering reached the blast site and chanted slogans against extremists and in favour of revolution.A bomb disposal squad also reached the spot to examine nature of the blast and the explosive material used in the incident.Reportedly, 2 to 4 kilogram explosive was used in the remote-control blast. The blast was very much similar to the previous ones which occurred in Abbas Town and Orangi Town areas in Muharram-ul-Haram. Witnesses said the motorbike carrying the bomb had been parked near the buses of Orangi Town sector. It is worth mentioning that it was very difficult for the terrorists to enter Jinnah Ground close to the MQM headquarters as MQM itself made security arrangements and did not allow even a single person without checking.Sindh Health Minister Dr Shagir Ahmed, talking to newsmen at Abbasi Shaheed Hospital, confirmed that at least four men were killed and 42 wounded. Earlier, a 3-kg explosive device was found from Bukhari Colony, Orangi Town, near Ghaghar Phatak, on Tuesday morning, in the Bin Qasim police area.