At least 21 people were killed on Friday and many others injured in different parts of the metropolis, bringing death toll to 90 in the recent waive of ethnic violence stared on Tuesday in Karachi. At least three people were killed and several others injured when unknown armed men opened fire on a passenger bus near Hasan Square. Reports said two armed groups were battling in the adjacent Sabzi Mandi and Esa Nagri areas. Unknown miscreants hurled a hand grenade in Bheem Pura area of Rinchor Line, killing three and injuring four others. According to sources, three people were killed in Landhi and 3 in Qasba Colony and adjacent areas. Two people were killed in Baldia Twon while many others were injured in Sultanabad, Nazimad, and Shah Faisal Colony.