BOMB attacks targeting election offices in Pakistan have killed six people and injured nine others, in the latest violence ahead of historic polls next month.

Five people were killed and eight injured late Thursday in Pakistan's commercial hub port city of Karachi when a bomb exploded outside the office of the secular Muttahida Qaumi Movement (MQM) party, police said.

MQM was a coalition partner in the recent government and has been threatened by Pakistan's umbrella Taliban faction.

Party spokesman Qamar Mansur told AFP the office was closed following a bomb blast on Tuesday that killed four people.

"All the victims were standing outside the office when the bomb exploded," he said.

Earlier in the day, a grenade attack on an election office in southwest Pakistan killed one person and injured another, officials said.

Senior government official Shah Irfan said two men riding a motorcycle threw the grenade at the election office of Sardar Umar Gorgage, a provincial leader in the Pakistan People's Party (PPP), which is seeking re-election at the ballot box on May 11 after five years in power.

There was no immediate claim of responsibility but Pakistan's umbrella Taliban faction has directly threatened the outgoing coalition partners, the PPP, Awami National Party and MQM, which are perceived as secular.

Deadly attacks targeting politicians or political parties have killed 34 people since April 11, according to an AFP tally.

May 11 national polls should see power pass from a civilian government that has served a full term to another through the ballot box for the first time in the nuclear-armed country's turbulent history.