US President Barack Obama hit back Friday at accusations that the White House was somehow involved in leaking classified national security secrets, labeling the allegations "offensive."

Lawmakers have fumed this week over a series of news reports, some quoting anonymous administration officials, that reveal details of covert US operations. Some Republicans have suggested the information was leaked to boost Obama's image of a tough commander-in-chief in an election year.

"The notion that my White House would purposely release classified national security information is offensive," Obama said. "It's wrong. And, you know, people I think need to have a better sense of how I approach this office and how the people around me here approach this office."

Several explosive stories have emerged recently, including Obama's push for cyber attacks on computers that run Iran's nuclear facilities; an apparent "kill list" of counterterrorism targets against whom Obama has authorized lethal action; and a secret drone campaign against terrorists in Yemen.

The New York Times reported that sources for their articles on the covert programs included former or current administration officials.

"We're dealing with issues that can touch on the safety and security of the American people, our families, or our military personnel, or our allies. And so we don't play with that," Obama said.

"Whether or not the information they received is true, the writers of these articles have all stated unequivocally they didn't come from this White House, and that's not how we operate."

Later Friday Attorney General Eric Holder announced the appointment of two US attorneys to lead a criminal investigation into possible wrongdoing over the leaks.

The "highly-respected and experienced prosecutors will be directing separate investigations currently being conducted by the FBI," Holder said in a statement.

"I have notified members of Congress and plan to provide more information, as appropriate, to members of the Judiciary and Intelligence Committees," Holder said.

"The unauthorized disclosure of classified information can compromise the security of this country and all Americans, and it will not be tolerated," he added.

Senator John McCain, who lost the 2008 presidential race to Obama, has been leading the accusations and received backing Thursday from Peter King, chairman of the House Homeland Security Committee.

"It has to be for reelection," King told Politico magazine about the leaks. "They can deny it all they want. But it would require a suspension of belief to believe it's not being done for political purposes."

Senate Select Committee on Intelligence chair Dianne Feinstein has called on Congress to swiftly enact legislation tightening rules to prevent unauthorized breaches, and welcomed an investigation launched by the FBI.

But she has held back on calling for a special prosecutor to look into the leaks, a move the White House has said Obama will not agree to.

Obama's Republican White House rival, Mitt Romney, believes the president should take greater charge in order to stop the leaks in their tracks.

"Leadership starts at the top. It's his sincere hope that the president is using all means at his disposal to put an end to this harmful practice," Romney campaign spokeswoman Amanda Henneberg told AFP on Thursday.