The first blast, apparently caused by a low-intensity device, occurred near an imambargah or Shia prayer hall in Qasba Colony area of Karachi shortly after 9.30 pm. Minutes later, another explosion occurred near the election office of the MQM.
Police officials said the second blast was caused by an explosive device planted in a truck. The MQM office was closed at the time of the blast.
The second blast damaged the MQM office and several nearby buildings and vehicles.
The bombings were the latest in a series of attacks on secular parties like the MQM and Awami National Party in Karachi over the past few days. Eleven people were killed yesterday when a senior ANP leader was targeted in a bomb attack.
Two bomb attacks targeting as many MQM election offices have killed at least 10 people. The MQM closed all its election offices across Sindh province following the attacks.