KARACHI (AFP) – Grief-stricken relatives demanded Wednesday that Pakistan investigate the torture and murder of an investigative journalist whose disappearance was blamed on the country's shadowy intelligence services.

Saleem Shahzad, a 40-year-old father of three, vanished after leaving home in Islamabad to appear on a television talk show, two days after writing an article about links between rogue elements of the navy and Al-Qaeda.

Shahzad carved out a career writing about the plethora of Islamist militant networks operating in Pakistan, and warned human rights campaigners before his disappearance that he had been threatened by the Inter-Services Intelligence.

Shahzad's body was found Tuesday, about 150 kilometres (93 miles) southeast of Islamabad. Police said it bore marks of torture.