TEHRAN - A prominent Iranian nuclear scientist was killed Monday and a second was seriously wounded in nearly simultaneous car bomb attacks in the Iranian capital, the semiofficial Fars news agency reported.

The explosions, which took place near Shahid Beheshti University, are the latest in a string of recent assassination attempts in which five doctors and professors have been killed in Tehran.

Iranian authorities blamed agents of Israel and the United States for the killings, saying they want to cause chaos in the country. But leading figures in Iran's opposition movement accused the government of plotting the attacks in order to spread fear in the capital, where many oppose the regime of President Mahmoud Ahmadinejad.

"Undoubtedly the hand of the Zionist regime and Western governments is involved" in the attacks, Ahmadinejad told reporters in a news conference. He said the bombings would not stop Iran from pursuing its nuclear program.

According to Fars, scientists Majid Shahriari and Fereydoun Abbasi were parking their cars in separate locations near the university campus about 7:45 a.m. local time when they were attacked.

Witnesses said each car was approached by a group of men on motorcycles, who attached explosives to the vehicles and detonated them seconds later, the news agency reported. Shahriari was killed instantly. Abbasi was wounded. Both men were with their wives, who were wounded as well.

Abbasi is a high-ranking Defense Ministry official who is involved in Iran's nuclear program. He has been subject to foreign travel restrictions since 2007 in accordance with United Nations Security Council sanctions and is considered a main player in Iran's nuclear and ballistic missile program.

The head of Iran's nuclear energy program, Ali Akbar Salehi, visited Abbasi in the hospital after the bombing and spoke to reporters about the scientists, the Islamic Republic News Agency reported.

Salehi said Shahriari was "in charge of one of the biggest projects" of Iran's nuclear program, the agency said, but it did not specify which program.

"The enemy took our dearest flower, but must know that this nation, through resistance and all its might, will make efforts to remove problems and achieve its desires," Salehi said.

Shahriari also was known for his involvement in a regional, non-nuclear scientific research project - called Synchrotron-light for Experimental Science and Applications in the Middle East, or SESAME - in which Israel also participated. He is the second Iranian scientist involved in that program to be assassinated in Tehran.

The SESAME project is based in Jordan, under the auspices of the United Nations. It includes scientists from several Middle Eastern countries. The involvement of both Iran and Israel makes the project unusual, because Israel is not recognized by Iran and has no ties to the Islamic Republic. Palestinian scientists also participate.

Iranian and foreign scientists say the project has applications in industry, medicine, nanotechnology and other fields unrelated to nuclear power.

In January, another scientist involved in the SESAME project, Massoud Ali-Mohammadi, was killed in Tehran when a bomb attached to a motorcycle exploded in front of his house.

At the time, many thought Ali-Mohammadi had been supporting the opposition. Government officials, however, accused the United States and Israel of being behind the attack.

Fars, which has close ties to Iran's Revolutionary Guard Corps, alleged that foreign "enemies" were involved in Monday's attacks - a charge Ahmadinejad echoed hours later.

"The enemies of the Iranian nation, who have lost hope in their pressure and sanctions projects, have once again, on the eve of negotiations with Iran, resorted to blind terrorist attacks so that they can advance their illegitimate and oppressive demands against the Iranian nation at the negotiating table," the agency wrote.

Iranian officials are supposed to meet with representatives of other nations Dec. 5 for talks on nuclear and other issues.