World powers will meet Iranian top representatives to discuss the Islamic state's disputed nuclear program in Istanbul at the end of January, a Russian official said on Thursday.

The so-called "P5+1" nations -- Iran and the five permanent U.N. Security Council members along with Germany -- had not all met since a June meeting in Moscow.

A prisoner swap of 48 Iranians held hostage by Syrian rebels in exchange for more than 2,000 people detained by Damascus "exposes the extent of the Syrian regime's dependence on Tehran," a main opposition group said on Thursday.

"The Syrian regime is so shameless that it is the only regime in the world that exchanges its own citizens' freedom for the freedom of citizens of foreign states," said the Syrian National Council.

U.S. financial institutions are being pounded with high-powered cyber attacks that some suspect are being orchestrated by Iran as payback for political sanctions.

"There is no doubt within the U.S. government that Iran is behind these attacks," James Lewis, a former official in the state and commerce departments and now a computer security expert at the Center for Strategic and International Studies, told the New York Times.

U.S. Defense Secretary Leon Panetta and his Israeli counterpart Ehud Barak met Wednesday for a meeting that underscored a "strong US commitment to Israel's security," the Pentagon said.

U.S. Defense Department spokesman George Little said in a statement that the two men "discussed a range of issues, and expressed their commitment to ensuring continued cooperation on many important regional issues -- particularly Syria, Iran, and Gaza."

Iran's sole nuclear power plant is now linked to the national energy grid at full capacity after having to be taken off-line for two months, the Iranian Atomic Energy Organization said on Wednesday.

"There are no particular problems," organization head Fereydoon Abbasi Davani told state television.

Chuck Hagel, the nominee for the next U.S. defense secretary, will seek to rein in Israel over any attempt to carry out a unilateral strike against Iran's nuclear facilities, Israeli observers believe.

Hagel's nomination by U.S. President Barack Obama must still be confirmed by the U.S. Senate, but the prospect of the former senator assuming the top Pentagon post has already stirred concern in Israel.

Iran said on Wednesday that it held "very constructive" talks with Argentina last week over long-standing accusations of Iranian involvement in a deadly 1994 bombing of a Jewish aid group in Buenos Aires.

Iranian Foreign Minister Ali Akbar Salehi met his Argentine counterpart Hector Timerman in Zurich, Switzerland, last Thursday to discuss the accusations leveled against eight Iranians, including top regime officials, the foreign ministry said on its website.

An Iranian convicted in the United States for smuggling equipment that under U.S. law could be used for Iran's nuclear program has returned home after serving a three-year sentence, media reported on Sunday.

Amir Hossein Seirafi, presented as a businessman by Iranian media, was arrested in January 2010 in Frankfurt, on charges of smuggling specialized vacuum pumps to Iran in violation of U.S. sanctions.

Air pollution in Tehran has left 4,460 people dead in a year, an Iranian health official said in reports Sunday, with another sounding the alarm over high dose of carcinogens in domestically-made petrol.

Hassan Aqajani, an adviser to the health minister, made the announcement on state television, and said the Tehran residents died in a year-long period since March 2011.

Iran's parliament on Sunday urged "judicial action" against police officers involved in the death in detention of a blogger last year, adding he may have died of "shock."

"The most likely cause of death could be shock, which, if proved, could have been caused by blows to sensitive parts of the body, or could have been due to excessive psychological pressure," media reported quoting a report read in the parliament.