UNITED NATIONS - Iran has called on the United Nations to condemn the  killings of Iranian nuclear scientists, which it said were “cruel, inhumane and criminal acts of terrorism.”

In a letter to Secretary-General Ban Ki-moon released on Wednesday, Iran’s UN Ambassador Mohammad Khazaee appealed to him and the Security Council “to condemn, in the strongest term, these inhumane terrorist acts and to take effective steps towards elimination of terrorism in all its forms and manifestations.”

“There is firm evidence that certain foreign quarters are behind such assassinations,” the ambassador said. “It is highly expected from the Secretary-General of the United Nations, and President of the Security Council of the United Nations as well as all other relevant organs and bodies to condemn, in the strongest term, these inhumane terrorist acts.”

Mostafa Ahmadi Roshan, a nuclear scientist, was killed in a blast in Tehran on Wednesday morning, the latest in a series of attacks against such scientists in recent years.

A motorcyclist placed a magnetic bomb under Roshan’s Peugeot 405. Two other scientists were killed in a similar fashion in the capital city in the last two years.

Khazaee, the Iranian ambassador,  blamed Israel for the attacks during an interview with CNN Wednesday night. Israel and the United States have threatened military action against Iran to force it to abandon its nuclear programme. Tehran insists it nuclear programme is for peaceful purposes. 

“They are trying to assassinate the Iranian scientists to deprive Iranians from the right of using peaceful nuclear energy,” Khazaee said. “We believe that these terrorist attacks are supported by some elements — especially within the Israeli regime as well as some quarters around the world.”

On Wednesday, US Secretary of State Hillary Clinton, rejected Iran’s claims.

“I want to categorically deny any United States involvement in any kind of act of violence inside Iran,” she said.

“We believe there has to be an understanding between Iran, its neighbors and the international community that finds a way forward for it to end its provocative behavior, end its search for nuclear weapons and rejoin the international community and be a productive member of it.”

Israel does not normally comment on such claims. However, Brig. Gen. Yoav Mordechai, a spokesman for the Israel Defence Forces, said on his Facebook page Wednesday: “I have no idea who targeted the Iranian scientist but I certainly don’t shed a tear.”

Roshan, 32, was a deputy director for commercial affairs at the Natanz uranium enrichment facility in Isfahan province and a graduate of Iran’s Oil Industry University, according to the semi-official news agency Fars.

Natanz, which is said to have 8,000 centrifuges in operation, is one of two facilities that is enriching uranium in the country. This week, the IAEA identified the second in the mountains of Qom province.

Officials in the United States and other Western nations have ratcheted up sanctions against Tehran since a November report by the IAEA said the Iranian government was developing the technology needed to build a nuclear weapon. Last month, US President Barack Obama announced sanctions against Iran’s central bank.