Iran's Intelligence Minister Heydar Moslehi has said Jundollah leader Abdolmalek Rigi had been in a U.S. military base 24 hours before his arrest by Iranian security forces.
He said Rigi was also carrying an Afghan passport supplied by the United States and had earlier visited European countries, according to state-run Press TV.
"Iranian claims that Abdolmalek Rigi was at a U.S. military installation prior to being apprehended are absolutely false," said Geoff Morrell, Pentagon press secretary.
He added that accusations that Washington supported Sunni extremist groups like Jundollah (God's soldiers) were "nothing more than Iranian propaganda."
"Allegations that we played some role in creating or supporting Jundollah is just another false claim in a long list of ridiculous Iranian fabrications," Morrell said.
Jundollah has claimed responsibility for an October 18 bombing that killed more than 40 Iranians, including 15 from the elite Revolutionary Guards.
The group operates in Iran's southeastern province of Sistan-Baluchistan, bordering Pakistan and Afghanistan.
Pakistan's ambassador to Tehran, Mohammad Abbasi, has said the arrest could not have occurred "without Pakistan's help."
Iran's accusations that Jundollah operated from bases in Pakistan's Baluchistan province have been a cause of friction with Islamabad and Rigi's arrest could go some way to easing those tensions.
(Reporting by Phil Stewart; editing by Todd Eastham)
