The corpses were lying near the shrine of Ayub Shah Bukhari, considered a saint by Sufi Muslims. Three of the dead worked at the shrine while the others were frequent visitors.

Police said a note reading "Stop visiting shrines -- from the Pakistani Taliban" was found at the scene along with a bloodstained knife.

The Taliban denounce worship at shrines as a grave sin and have carried out many deadly bomb and suicide attacks against Sufis in recent years.

Five of the six victims were later identified as Munwar, Jinn,Saleem, Ramzan, and Abid.

In one of the bloodiest episodes, at least 50 people were killed in April 2011 in a suicide attack on a shrine in the city of Dera Ghazi Khan.

But senior police officer Amir Farooqi voiced caution over the note, telling AFP he would not draw any conclusions until further investigation.

Police have detained some suspects including the 'Mutwali' (trustee) of the shrine Ayub Shah Mazar Mr Jumman Shah and his assistant.

The bloodstained knife has been sent for forensic tests.

Karachi, Pakistan's economic hub, has been plagued for years by ethnic, political, sectarian and criminal violence. (AFP)

SOURCE: AFP