The Islamic militant group blamed by officials for the attack that killed Bhutto denied any links to the killing on Saturday, and Bhutto's aides accused the government of a cover-up.
President Pervez Musharraf ordered his security chiefs to quell rioting by Bhutto's grieving followers that has killed at least 44 people over three days and caused tens of millions of dollars in damage.
"Criminals should stop their despicable activities, otherwise they will have to face serious consequences," Interior Ministry spokesman Javed Iqbal Cheema said.
Democratic presidential candidate Hillary Rodham Clinton said Friday that an international probe was vital because there was "no reason to trust the Pakistani government," while others called for a U.N. investigation.
Cheema dismissed the suggestion.
"This is not an ordinary criminal matter in which we require assistance of the international community. I think we are capable of handling it," he said. An independent judicial investigation should be completed within seven days of the appointment of its presiding judge, he said.
White House spokesman Tony Fratto said Pakistan had not asked the United States for help.
"It's a responsibility of the government of Pakistan to ensure that the investigation is thorough. If Pakistani authorities ask for assistance we would review the request," he said.
I have no doubt they are "capable of handling it." Yeah, right.