A Pakistani spokesman has denounced comments by the top-ranking U.S. military officer that the Pakistani government apparently sanctioned the killing of a journalist in late May.

An unnamed Pakistani government spokesman told the state-run Associated Press of Pakistan that Admiral Mike Mullen's ((chairman of the Joint Chiefs of Staff) statements were ” extremely irresponsible.”

The spokesman said Pakistan has established an independent panel to investigate the death of Pakistani reporter Saleem Shahzad.

Mullen said Thursday while he could not tie the death to Pakistan's powerful intelligence service, he has not seen anything to counter reports that Islamabad approved the beating death of Shahzad. Pakistan's Inter-Services Intelligence agency has said the allegations are “baseless.”

Shahzad, who worked for the Hong Kong-based Asia Times Online, disappeared from Pakistan's capital Islamabad on May 29. His body was found in a canal two days later bearing signs of torture.

Before his death, Shahzad had been investigating alleged ties between Pakistan's military and Islamist groups. He reported that al-Qaida militants had attacked a Pakistani naval base after talks failed to secure the release of two naval officials arrested on suspicion of links to the global terror network.

Mullen acknowledged U.S. relations with Pakistan are “under extraordinary pressure.”

He said Islamabad's already fragile bond with Washington became severely strained when U.S. special operations forces killed al-Qaida leader Osama bin Laden in a raid on his compound deep into Pakistan in May.