Two paramilitary troops were killed and 10 others were injured in three separate blasts in Pakistan's southern port city of Karachi on Wednesday, local media reported. Dunya TV said that in the latest attack, one man was killed and five including four paramilitary troops, Rangers, were injured when a bomb went off near the Rangers Headquarters in Nazimabad area of Karachi, the capital city of the country's south Sindh province. Nature of the blast has not been confirmed by officials yet, however, local media reported that the explosion was carried out by a suicide bomber who blew up himself when security personnel stopped him at a security picket near the Rangers Headquarters. Earlier in the morning, some unknown militants hurled two hand grenades one after another at Rangers' check post in Nazimabad area of Karachi, killing one troop and injuring five others. Police said that the injured troops were shifted to a nearby hospital where one of them was in critical condition. The attackers fled the scene after the attack and police kicked off a search operation in the area. No group claimed responsibility for the attack yet. Meanwhile on Wednesday morning, police and rangers arrested over 20 suspected militants in raids in various areas of the city.