Five female Pakistani polio vaccination workers have been shot dead in a string of co-ordinated attacks - four within 20 minutes across Karachi, BBC News reported.

The fifth woman was shot and wounded in the city of Peshawar in the north-west and later died of her injuries.

A UN-backed programme to eradicate polio - which is endemic in Pakistan - has been suspended in Karachi.

No group has said it carried out the shootings, but the Taliban have issued threats against the polio drive.

"These were pre-planned and co-ordinated attacks in various localities which took place within a span of 20 minutes," Imran Javed, a police spokesman told the BBC of Tuesday's attacks in Karachi.

Earlier reports said a male health worker had been shot dead in Karachi on Monday, but officials now say his death was not related to the polio vaccination drive.