Pakistan's spy agency Inter-Services Intelligence (ISI) denied the allegations that its operatives were behind the abduction and killing of the whistle-blower journalist Syed Saleem Shahzad.

An ISI official denied that the agency had threatened the journalist and described his death as ''unfortunate and tragic'' also added that this is a ''source of concern for the entire nation.''

The intelligence official, who was unnamed, has made the comments to the government news agency Associated Press of Pakistan.

Shahzad, who had extensively reported on terrorism issues, was buried in his hometown, Karachi, on Wednesday. He was abducted from Islamabad, on Sunday evening and his body was found 100 miles away.

Doctors who examined his body in Islamabad said it bore signs of torture and marks of beating, reports say.

Human Rights Watch said that Shahzad had received repeated threats from Pakistan's intelligence agencies over the past three years and that the abduction bore all the hallmarks of the ISI, which has been accused of multiple human rights abuses against journalists and political activists in Pakistan, reports Reuters.

ISI said it was regrettable that some sections of the media had leveled such allegations against the agency. It called on them to act responsibly and suggested that it may consider taking legal action against them.

The official said that a meeting between ISI officials and Shahzad in October was part of the media wing's mandate to keep in touch with members of the media and that it represented nothing sinister.

The ISI has offered its deepest condolences to the family and assured them that it will leave no stone unturned in helping to bring the culprit to justice.