A blast in Pakistan's commercial hub, Karachi, has injured at least seven people in the run-up to the May 11 parliamentary elections.

Thursday's explosion happened outside the offices of the Muttahida Quami Movement (MQM) party on Burns Road, a central location with many shops and restaurants.

MQM is secular party that was a coalition party in Pakistan's outgoing ruling coalition.

The blast is the latest in a series of attacks on offices of secular political parties contesting the elections.

Officials said the casualty toll could rise as the blast was large.

A local police official said the bomb was planted in the ablution room of a Sunni Muslim mosque close to the MQM office.

Security services and ambulances rushed to the scene and the injured were taken to hospital.

Three bombs, two of which targeted MQM and the Pakistan Peoples Party (PPP), killed three people and wounded 49 others in Karachi on Saturday.

At least 61 people have been killed in attacks on politicians and political parties since April 11, according to a tally by the AFP news agency.

The Pakistani Taliban has vowed to disrupt the elections and claimed responsibility for some of the attacks.

Source: Agencies