At least 16 persons were killed and over 50 others, including media persons, were injured in a strong explosion near the Punjab provincial assembly here on Monday.The explosion took place at Charing Cross, Mall Road, in Lahore when a large group of chemists and pharmaceutical manufacturers was protesting in front of the assembly complex. There was a significant presence of law enforcers in the area due to the protest.Deputy Inspector General (Traffic) Lahore Capt (retd) Ahmad Mobin and Senior Superintendent of Police Zahid Mehmood were among the dead, and reports said more casualties were expected among law enforcement personnel who were present at the spot.Hours earlier, Traffic Police chief had been seen on television mediating with protesters who had gathered at the site.Capt. Mobin was talking to protesters to call off the protest and clear the area.Punjab Law Minister Rana Sanaullah, confirming the blast, said the police failed to maintain a high-level security due to massive presence of protesters."It is premature to say anything about the nature of the blast and the exact number of injured people," he added.Rescue services, including ambulances and fire tenders, have rushed the spot and are shifting the injured to Mayo Hospital and Ganga Ram Hospital.No group has claimed the responsibility for the attack yet.Lahore was the site of an Easter Day bombing last year that killed more than 70 persons gathered in a public park.