A blast took place in the Lyari area of Bloody Karachi on Friday that killed three and injured at least 27 others, DawnNews reported.The injured were immediately shifted to civil hospital.
Motorbike riders threw a grenade in a narrow lane of the city's congested Chakiwara area, senior police official Javed Baluch told AFP.
Police officer Iqbal Mahmood said the attack happened near a roadside restaurant which residents said was close to a gambling den.
"Three people were killed and 20 maimed in the blast, which was triggered by a hand bomb," senior home ministry official Sharfuddin Memon told AFP.
"We are investigating if the attack was the result of rivalry between criminal gangs or involvement of bad turbans." The area is known for festivities between rival criminal gangs, drug peddlers and gamblers, police said.
Last month 20 people were killed and around 40 maimed when a bomb destroyed an illegal gambling den in Bloody Karachi.
Doctor Mubarak Ali of the main Civil Hospital told AFP by telephone that more than 15 people were receiving treatment after Friday's attack.