"This statement is tantamount to interference in our sovereignty. Pakistan will not allow anyone to interfere in its national affairs," Gilani said, referring to recent comments of Mullen, the US Joint Chiefs of Staff Chairman.
However, Gilani, during an interview with a TV news channel, said if the US had any proof regarding involvement of Pakistan government or establishment in Shahzad's murder, it should be presented to the independent commission headed by a Supreme Court judge that is probing the incident.
Shahzad was abducted while driving from his house to a TV station in Islamabad on May 29, two days after he alleged in an article that al-Qaeda had infiltrated Pakistan's Navy.
His body, bearing marks of torture, was found the next day in a canal in Punjab province. Journalists' associations and rights groups alleged intelligence agencies were responsible for the killing, a charge denied by the ISI.
Shahzad had also told colleagues about receiving veiled threats from the ISI. Mullen's comments were the first public remarks by a senior American official linking Pakistan government to the killing.