Iranian state media are raising the specter of revenge assassinations on Israeli and possibly Western targets in response to the killings of nuclear scientists that Iran has blamed on Israel and the U.S., the latest development in an escalating, multiple-front war of words.

The U.S. has denied any involvement in the violence, most recently the bomb blast Wednesday that killed Iranian scientist Mostafa Ahmadi Roshan, while Israeli officials have hinted at covert campaigns against Iran without directly admitting involvement. Iranian leaders, meanwhile, have vowed to take their complaints to the United Nations while at the same time agreeing to open their nuclear facilities to outside inspectors.

Recent Iranian wargames near the Strait of Hormuz have further increased tensions in the region and with the U.S., given that the straight is a strategic oil route and that Iran has threatened to block it if provoked.

And it didn't help relations this week when Iran announced a joint U.S.-Iranian national will be executed after being found guilty of spying -- a charge both he and Washington denies.

As for the threat of retaliation for the scientist killings -- at least four in two years -- the most incendiary rhetoric appears to be mostly contained to Iranian state media. 

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A column in the Kayhan newspaper by chief editor Hossein Shariatmadari asked why Iran did not avenge Roshan, a chemistry expert and a director of the Natanz uranium enrichment facility, by striking Israel.

"Israeli military chief Lt. Gen. Benny Gantz in his recent remarks spoke about damaging Iran's nuclear program," he wrote. "Assassinations of Israeli military and officials are easily possible."

Other publications have made similar calls for retaliation. Official reaction from the Iranian government, on the other hand, has been more tempered.

In a letter to the U.N. secretary-general on Thursday, Iran's U.N. Ambassador Mohammad Khazaee called on the U.N. to condemn the killing and two earlier attacks that left two nuclear scientists dead and another seriously injured.

"There is firm evidence that certain foreign quarters are behind such assassinations. As has been claimed by these circles, such terrorist acts have been carried out as part of the efforts to disrupt Iran's peaceful nuclear program, under the false assumption that diplomacy alone would not be enough for that purpose," the letter read in part.

U.S. Secretary of State Hillary Clinton denied any U.S. role in the killing and the U.S administration condemned the attacks.

At the same time, diplomats said Thursday that a senior U.N. nuclear agency team will visit Tehran on Jan. 28, with Iran saying it is ready after years of refusal to discuss allegations that it was involved in secret nuclear weapons work.

Diplomats have previously said that International Atomic Energy Agency officials were discussing such a trip with their Iranian counterparts. But before the diplomats' comments Thursday, no date -- or indication that Iran was ready to talk about the allegations -- had been mentioned.

Any follow-through on the part of Iran on its reported pledge to discuss nuclear arms suspicions would be significant.

For more than three years, Tehran has blocked IAEA attempts to follow up on U.S. and other intelligence alleging covert Iranian work on nuclear arms, dismissing the charges as baseless and insisting all its nuclear activities were peaceful and under IAEA purview.

Faced with Iranian stonewalling, the IAEA summarized its body of information in November, in a 13-page document drawing on 1,000 pages of intelligence. It stated then for the first time that some of the alleged experiments can have no other purpose than developing nuclear weapons.
Iran continues to deny the charges and no change in its position is expected during the Tehran talks with IAEA officials. But even a decision to enter a discussion over the allegations would be a major departure from outright refusal to talk about them -- and create hopes of future progress in the investigation.

Two diplomats told The Associated Press that Iranian officials had suggested they were ready to talk about the issue during recent meetings with officials of the Vienna-based IAEA. They asked for anonymity because their information was confidential.

Iran denies it is trying to make nuclear weapons, saying its program is for peaceful purposes only and is geared toward generating electricity.

Those claims were called into question on Monday when the IAEA confirmed Iran had begun increasing its production of uranium enriched to 20 percent. That's a significantly higher concentration than the nation's main stockpile -- and can be turned into weapons-grade material more quickly than the lower enriched uranium.

The Associated Press contributed to this report.