Firefighters work at the scene of a bomb blast in northern Tehran Tuesday. ((Associated Press))

A Tehran University nuclear physics professor killed Tuesday by a remote-controlled bomb outside his home had publicly backed Iranian opposition leader Mir Hossein Mousavi but was not considered a political figure, state media reported.

Massoud Ali Mohammadi, 50, had just left his house on his way to work when the remote-controlled explosion went off, state-run Press TV said.

Iran's semi-official ISNA news agency quoted Tehran prosecutor Abbas Jafari Dolatabadi as confirming the killing and saying no one has been arrested.

Iran's Foreign Ministry accused Israel and the U.S. of involvement, according to the state TV website.

"In initial investigations, there are some indications of vices of the Zionist regime, the U.S. and their mercenaries in Iran in the terrorist incident," ministry spokesman Ramin Mehmanparast was quoted as saying in the report.

Before last summer's hotly disputed presidential elections, Ali Mohammadi's name was among a list of 240 Tehran University teachers who threw their support behind reformist leader Mousavi.

Nuclear physics professor Masoud Ali Mohammadi was killed after a bomb blast in front of his house, in northern Tehran's Qeytariyeh neighbourhood, state media reported. ((Fars News Agency/Associated Press))

Although Ali Mohammadi was among a list of opposition supporters, a Tehran University official told the Mehr news agency he was not actively involved in politics.

"The prominent professor was not a political figure and had no activity in the field of politics," Mehr quoted Ali Moqari, head of the university's science department, as saying.

Ali Mohammadi also had no involvement in Iran's atomic agency, according to spokesman Ali Shirzadian. Iran has faced increased scrutiny from the United States and the United Nations over its pursuit of a nuclear enrichment program.

In 1992, Ali Mohammadi received the first doctorate in nuclear physics to be awarded in Iran, from Tehran's Sharif University of Technology.

Officials at both Tehran University and Iran's nuclear agency said his work was primarily in the realm of quantum and theoretical physics.