U.S. State Secretary Hillary Clinton on Wednesday denied that the United States was involved in the assassination of an Iranian nuclear staff and urged Iran to end its provocative behavior, including threatening to close the Straits of Hormuz.

"I want to categorically deny any United States involvement in any kind of act of violence inside Iran," Clinton said at a press conference at the State Department alongside visiting Qatari Prime Minister and Foreign Minister Sheikh Hamad bin Jassim al-Thani.

Clinton's remarks came after a bomb attack killed an Iranian nuclear site staff and his driver in northern Tehran on Wednesday. Local reports said that the passenger being killed, identified as Mostafa Ahmadi-Roshan, was the deputy chief of Iran's Natanz nuclear enrichment site's commercial section.

A number of Iranian nuclear scientists have been assassinated in recent years. Iran's First Vice President Mohammad-Reza Rahimi said Wednesday that Israeli agents were the perpetrators of Ahmadi- Roshan's assassination, local media reported.

At the press conference, Clinton again urged Iran to "end its provocative behavior, end its search for nuclear weapons, and rejoin the international community and be a productive member of it."

She also talked about the threatening by Iran to close the Straits of Hormuz, one of the world's most critical oil route, reaffirming the U.S. commitment to keep it open.

"It's part of the lifeline that keeps oil and gas moving around the world," said Clinton. "And it's also important to speak as clearly as we can to the Iranians about the dangers of this kind of provocation."

VietNamNet/Xinhuanet