At least 135 people have been detained over an armed attack on a bus in Karachi which claimed 46 lives, media reported on Friday.Raids were carried out by the Pakistan Rangers and police in different parts of Karachi late Thursday night until early Friday morning, Geo News reported.Sources said a unit-in-charge of a political party was among those detained. The detained individuals have been shifted to a yet undetermined location for interrogation.At least 46 people were killed in the attack on Wednesday when gunmen opened indiscriminate fire inside a bus carrying people of the Shia Ismaili community.Prime Minister Nawaz Sharif has termed the attack as an act of cowardice and vowed that the culprits would be dealt with very strictly.