Thirty-one Republican senators have sent a letter to U.S. Attorney General Eric Holder, demanding for a special counsel to investigate the suspected security leaks from President Barack Obama's administration, local media reported Tuesday.The lawmakers called the national security leaks reportedly made by Obama administration's senior officials in recent months " stunning," according to thehill.com, website of the Capitol Hill newspaper The Hill."If true, they reveal details of some of our nation's most highly classified and sensitive military and intelligence matters, thereby risking our national security, as well as the lives of American citizens and our allies. If there were ever a case requiring an outside special counsel with bipartisan acceptance and widespread public trust, this is it," the letter said.U.S. media disclosed earlier the month that Obama personally approved a "kill list" of al-Qaeda operatives in Yemen, and a covert operation to thwart an al-Qaeda attack on U.S. airliner using underwear explosive device that could not be picked up by airport scanners. The New York Times also reported that Obama ordered stepped-up cyberattacks on Iran's nuclear program months after taking office, significantly expanding America's first sustained use of cyberweapons.The Republican lawmakers also singled out National Security Adviser Thomas Donilon as a likely source of leaks in New York Times reporter David Sanger's book, Confront and Conceal.Under pressure, Holder already appointed on June 8 two investigators to lead the probe into the leaks, which were regarded by the Republicans as an attempt by the Obama campaign to bolster his image on national security so to help him win the re- election.