Pakistan has faced a fresh blow to its polio eradication efforts and accusations of a cover up, after officials confirmed an outbreak of a virus strain thought to have been stamped out.

Seven children have been paralysed in recent months after being infected by a type of virus that was considered eradicated, but formerly used in vaccination campaigns.

Officials were accused of trying to hush up the outbreak, which comes as the country's eradication efforts were already faltering, with a nearly seven-fold jump in cases since 2018.

A source told the Guardian that rather than announce the new outbreak, senior officials decided on a secret vaccination campaign to target the new strain.