At least three people were killed and 20 others injured during a suicide bombing in Pakistan's Quetta city on Sunday, rescue teams said.The incident took place at about 7.30 a.m. when the bomber hit his explosive-laden motorbike into one of the vehicles of the Frontier Corps (FC) convoy, on the outskirts of the city, Muhammad Zeeshan, manager operations at the rescue department of Edhi Foundation Quetta, told Xinhua news agency.Police sources from the city told Xinhua that the FC convoy was assigned to provide security to the minority ethnic group of Hazara community in the city, and it was on its routine patrolling when it came under attack.The injured people including FC personnel and passers-by were shifted to a nearby hospital where several of them were said to be in critical condition, the rescue official said.After the investigation, the bomb disposal squad said that about 5 to 6 kg of explosives were used in the attack.No group has claimed the attack yet.The area has been cordoned off for further investigations.