(CNN) -- An explosion in Karachi, Pakistan, killed at least eight people and injured more than 20, Karachi authorities said late Friday.
The target of the blast, according to Salim Abbasi, a Karachi police official, was a meeting the the Awami National Party, an anti-Taliban liberal political party.
"It's unclear what caused the blast," said police spokesman Naeem Shah. Emergency personnel were on the scene of the explosion on Karachi's west side and an investigation was under way, he added.
The blast came as Pakistan prepares for elections next month.
Another liberal anti-Taliban party, Muttahida Quami Movement (MQM), was the target of a remotely detonated blast that killed two people and injured 18 others earlier in the week, Karachi police said.
In a call to CNN after that earlier attack, Taliban spokesman Ihsan Ullah Ihsan said his group claimed responsibility for the explosion.
An official of MQM, meanwhile, said the party would close its political offices across the country to protest the attack.
"(The) government failed to provide us security," said MQM Deputy Chief Farooq Sattar.
He added, "These coward attacks can't demoralize our workers ... We will defeat (the) Taliban by providing education to people."