The US criticized the release of nuclear scientist Abdul Qadeer Khan from house arrest in Pakistan on Friday and demanded assurances from the Pakistani authorities that he was not involved in sharing nuclear secrets. Pakistan said he no longer posed a risk because his smuggling network had been dismantled. "We have successfully broken the network that he had set up and today he has no say and has no access to any of the sensitive areas of Pakistan," Foreign Minister Shah Mehmood Qureshi said. "A.Q. Khan is history." US State Department acting deputy spokesman Gordon Duguid said Khan's release was "extremely regrettable" and accused him of still posing a threat. "This man remains a serious proliferation risk," Duguid said. "The proliferation support that Khan and his associates provided to Iran and North Korea has had a harmful impact on international security, and will for years to come." Khan, who helped Pakistan develop a nuclear weapon and admitted providing key nuclear information to Iran, Libya and North Korea, emerged from five years of de facto house arrest on Friday after a court declared him a "free citizen" subject to a secret agreement with the government. US Secretary of State Hillary Clinton also said she was "very much concerned" about the situation when asked about Khan's release at a photo op Friday. She said she would have more to say on the matter later. Earlier Friday, White House spokesman Robert Gibbs, like Duguid, said the administration was waiting for Pakistani authorities to confirm Khan's release but that US President Barack Obama wants "assurances that Dr. Khan is not engaged or involved in any of the activity that resulted in his house arrest earlier." Khan told reporters outside his home on Friday that government officials had reviewed his case with the Islamabad High Court and that there had been a "good judgment." Khan added that he could now "move around." However, prosecutor Amjad Iqbal Qureshi said "security measures" for Khan would remain in place. Khan was detained in December 2003, and admitted on television in early 2004 that he operated a network that spread nuclear weapons technology around the world. He was immediately pardoned by then-president Pervez Musharraf and placed under de facto house arrest.