TEHRAN - Iranian state TV on Thursday showed the footage of a US drone shot down by Iranian troops in the eastern region four days ago.

The Islamic Revolution Guards Corps' (IRGC) Aerospace Commander Brigadier General Amir-Ali Hajizadeh said in the report shown by IRIB TV station that "recently, with the help of collected intelligence and with the accurate electronic monitoring, it was learned that the drone was to enter Iran's air space for spying."

An undated picture received Dec 8, 2011 shows a US RQ-170 unmanned spy plane displayed in front of a flag with Persian script that reads "Down with the US (top), down with Israel and down with Britain (bottom)" at an unknown location in Iran. The unmanned US drone Iran said on Sunday it had captured was programmed to automatically return to base even if its data link was lost, one key reason that US officials say the drone likely malfunctioned and was not downed by Iranian electronic warfare. [Photo/Agencies]

"After the drone infiltrated Iran's eastern space, it was trapped by the electronic systems of Iran's armed forces and was downed with the least damage possible," Hajizadeh said.

Iranian media reported Sunday that the Iranian military downed a RQ-170 US reconnaissance drone aircraft in the eastern part of the country after finding it had transgressed the eastern borders.

The RQ-170 drone is an unmanned aircraft which has been used for reconnaissance and surveillance by the United States in Afghanistan.  

Describing the hi-tech specifications of the downed aircraft, the IRGC's aerospace commander said Thursday that the military experts are well aware that the drone has very invaluable technological data.

The drone, the technology of which has been used in B2 and F35 planes too, is equipped with highly advanced surveillance technology and electronic communication and radar systems, Hajizadeh said, adding that the drone is controlled both by satellite and stations based in Afghanistan and the Untied States.

Despite the Iranian claims, US officials denied that the drone was brought down by Iran, insisting that its fall was due to mechanical difficulties, the Wall Street Journal reported.

The US officials were quoted as saying on Wednesday that the United States had considered but finally given up a covert mission inside Iran to retrieve or destroy a stealth drone crashed last week, for fear that such actions could provoke explosive clashes with Iran.

US officials are concerned that the craft's falling into Iran 's hands could lead to security breach, although they said the aircraft's technology cannot be engineered with ease.  

The Iranian Foreign Ministry on Thursday summoned Swiss Ambassador to Tehran Livia Leu Agosti to protest the "violation" of its airspace by a US drone, the state IRIB TV reported.

Iran's protest letter denounced the growing US "provocative and secret moves" against the Islamic Republic, said the report.

"The move is in violation of all international conventions and runs counter to regional and international peace and security. Surely the responsibility for the illegal move lies with the US authorities," the letter was quoted as saying.

The letter added that Iran would reserve the right for following the case as deemed appropriate.

The Swiss embassy in Tehran represents the US interests in Iran since Tehran and Washington severed diplomatic relations in 1980.

US President Barack Obama said on Thursday that no options are off the table on Iran's nuclear program.

"No options off the table means I'm considering all options," the president told reporters at the White House.

In defense of his policy towards Iran, Obama said when he took office in 2009, the world was divided but Iran "was unified and moving aggressively on its own agenda."

In contrast, the Islamic Republic is isolated today while the world is unified and "applying the toughest sanctions that Iran's ever experienced," he argued, adding the sanctions are having an impact inside the country.

He vowed to work with US allies, including Israel, to prevent Iran from acquiring nuclear weapons.

"If they are pursuing nuclear weapons, then I have said very clearly that is contrary to the national security interests of the United States, it is contrary to the national security interests of our allies, including Israel, and we are going to work with the world community to prevent that," he said.

He challenged Iran to act "responsibly" and foreswear the development of nuclear weapons, saying the move would still allow the country "to pursue peaceful nuclear power."

Amid the rising tension between the West and Iran, and the military threats that comes from the United States and Israel against Iran, the Islamic Republic has claimed that it will react to any threat with threat.

Deputy commander of IRGC Brigadier general Hossein Salami said last week that in the face of Western military threats, the defense doctrine of the Islamic Republic would be "threat for threat."

However, Iran said that it is not in war alert with the United States or Israel.

Chief of Iran's Majlis (parliament) Defense Committee rejected on Wednesday media reports that the Islamic Republic has recently gone on war alert.

"Under the existing conditions, we have no indication that we should be in a particular and new military condition, and it is not correct that Iran's armed forces are placed on a specific alert," Gholam-Reza Karami said.

Karami said the country is always prepared for any military encounter, said the report.

Recently, some Western media reported that IRGC has issued a war alert "amid a series of mysterious blasts and cyber attacks" in the country.

The Daily Telegraph said the IRGC had started to deploy long- range missiles and guard units to key defensive positions around the country after an order from its Chief Commander General Mohammad-Ali Jafari.

On November 28, the IRGC commander Gholam-Reza Jalali dismissed media reports that a virus attack on Iran's missile program caused the two successive explosions in the garrison of IRGC which killed a senior IRGC commander and 16 of IRGC members some 35 km away from the Iranian capital of Tehran.

Some believed the intelligent services of Israel and the United States were behind the blast.

While the West accuses Iran of developing nuclear weapons under the guise of "civilian" nuclear program, Iran insists that its nuclear program is only for "peaceful" purpose.