Iran made a formal protest on Thursday over a U.S. drone entering "deep" into its eastern airspace last week, and aired footage of what appeared to be the downed aircraft on state television.

Swiss ambassador Livia Leu Agosti was summoned to the foreign ministry and told the incident suggests Washington has upped its "provocative and covert actions" against the Islamic regime, the state television website reported.

The establishment by the United States of an Internet-based "virtual embassy" for Iranians is an admission it should not have cut ties with the Islamic republic, the foreign ministry said Thursday.

The initiative will also fail in its intended aim of bringing Washington's message to the Iranian people, ministry spokesman Ramin Mehmanparast said in a statement published on the state television website.

The United States has a "very strong interest" in a successful outcome from the European Union summit starting later on Thursday, U.S. Treasury Secretary Timothy Geithner said during a visit to Italy.

"The U.S. and the world economy as a whole has a very strong interest in the success" of the summit, Geithner said following talks with Italian Prime Minister Mario Monti in Milan and after visits to France and Germany.

Prime Minister Vladimir Putin on Thursday accused the United States of stirring up controversy over Russia's polls and warned those protesting the result they would be punished if they broke the law.

After three days of protests against election results the opposition says were rigged, Putin said the authorities should enter into dialogue with the opposition. But he accused some of its leaders of acting selfishly.

A helicopter taking people on a luxury sunset tour of the Las Vegas Strip and Hoover Dam crashed into a mountainside Wednesday, killing the pilot and the four passengers on board, federal authorities said.

The aircraft operated by Sundance Helicopters collided into the River Mountains surrounding Lake Mead just before 5 p.m., said National Park Service spokesman Andrew Munoz. Numerous witnesses heard the crash and reported seeing smoke about 4 miles west of the lake's edge, Munoz said, and officials determined that all five people on board were killed.

A court in Thailand on Thursday jailed a Thai-born American for two-and-a-half years for defaming the monarchy -- a sentence that the United States criticized as "severe".

The conviction of Joe Wichai Commart Gordon -- who appeared in court in shackles -- is the latest in a series of cases under the kingdom's strict lese majestic laws, which rights campaigners say are used to stifle free speech.

Republican presidential hopeful Newt Gingrich said Wednesday that Pakistan's nuclear arsenal was at risk of being seized by "extremists" who had probably infiltrated Islamabad's military.

"My guess is that they have well over 100 nuclear weapons and that the Pakistani military is so penetrated by extremist elements you have no idea if one morning, they are going to lose three or four of them. I mean just have them stolen," Gingrich told CNN's Situation Room program.

The United States on Wednesday urged greater action by Pakistan against a Sunni Muslim militant group that Afghanistan blamed for an unprecedented massacre against its Shiite minority.

Afghan President Hamid Karzai said that the banned Pakistani extremist movement Lashkar-i-Jhangvi orchestrated the bloodshed Tuesday on the Shiite holy day of Ashura.

Iran on Wednesday blocked an Internet website the United States was touting as a "virtual embassy," and which one senior MP slammed as an attempt to deceive the Iranian people.

The address, http://iran.usembassy.gov/, was inaccessible inside Iran, instead showing a message in Farsi saying: "In accordance with computer crime laws, access to this website is not possible."

A U.S. adversary would currently be unable to bring down the entire U.S. electrical grid using cyber weapons but such a scenario is conceivable within two to five years, the former vice chairman of the Joint Chiefs of Staff said Tuesday.

"Today, the likelihood that a nation-state or any actor is going to knock down the entire electrical grid of a country, of the United States let's say, is very remote," retired General James Cartwright said.