Shahidullah Shahid, spokesperson of the Tehrik-e-Taliban Pakistan, said they carried out the blasts in Karachi to take revenge for the killing of 15 people in the Nov 21 US drone attack in Hangu district, Xinhua quoted the spokesman as telling the media.
Shahidullah Shahid said they would carry out more such attacks across the country if drone attacks are not halted.
8 people were killed and over 40 injured in Friday's blast
Two bombs were triggered off by a remote controlled device near Ancholi area of Karachi on Friday night, killing four people on the spot and injuring many others.
Another four people later succumbed to injuries at a hospital where doctors said the death toll may rise further as five to six people were still in critical condition.
Deputy Inspector General of Police Javed Alam Odho said an estimated three to four kg of explosives were planted in two motorbikes. The blasts were followed by a round of condemnation from various religious groups and political leaders including Syed Qaim Ali Shah, chief minister of Sindh province of which Karachi is the capital.