More than eight people have been injured in a series of parcel bomb explosions in Pakistan's largest city, Karachi.

Two of the parcel bombs were opened at police stations and a third at the provincial home secretary's office.

The bombs went off in quick succession in the centre of Karachi.

The Inspector-General of police in Karachi has warned all police stations not to touch any parcels they have received.

No one has said they were responsible for the parcel bombs and police have not yet speculated who might be behind them.

Earlier attacks

"Parcel bombs are relatively rare in Pakistan and this could mark a new phase of violence in the city", says the BBC Islamabad correspondent, Susannah Price.

An injured policeman seeks help after the explosion

Earlier this year there were two suicide bomb attacks in Karachi, both aimed at foreigners, one outside the American consulate and the other, which killed 14 people, most of them French nationals.

The parcel bombs appeared to be aimed at the Pakistani establishment.

They come nearly a week after Pakistan's general elections but it is not known if there is any link to, the still as yet, inconclusive outcome of these polls.

Last month police arrested a number of suspected Islamic extremists, one of whom was believed to have masterminded the two deadly suicide bomb attacks in Karachi.