At least six policemen were killed and about 50 others injured early Saturday morning when a police vehicle was attacked by unknown people in Pakistan's southern port city of Karachi, reported local Urdu TV channel Samaa. According to the local media reports, the attack took place in the wee hours of Saturday in the Chakragoth area of the city when a bus carrying an estimated 50-plus policemen in plain clothes was attacked by unknown people. During the attack, two assailants were also killed, said the reports, adding that four injured policemen were in critical condition. Local media quoted Pakistani Interior Minister Rehman Malik as saying the police attacked were on the way to carry out a search operation in the afore-said area when they came under attack.