A shutter down strike is being observed on Sunday in Quetta and other parts of Balochistan to mourn Saturday’s deadly blast which killed at least 83 people and injured over 190 others.The strike call was given by Majlis-e-Wahdat-ul-Muslimeen (MWM), Hazara Democratic Party, Shia Ulema Council, Quetta Yakjehti Council, Tehrik-e-Nifaz-e-Fiqah Jafria, Balochistan Shia Conference and others.Key business centers of the city remained closed on Sunday amid high security and patrolling in Quetta.The government of Balochistan has announced one-day while Shia organizations announced three-day mourning in the province.A suicide bomber rammed an explosive-laden water tanker in a packed bazaar near Hazara town, an area dominated by Shias on the outskirts of Quetta, at around 6:00 pm (local time) on Saturday.Last month three bomb blasts in Quetta killed nearly 100 people, one of Pakistan's worst sectarian attacks. Thousands of Shi'ites protested in several cities after that attack.