91Èȱ¬

Iranian TV has shown the first video footage of an advanced US drone aircraft that Tehran says it downed 140 miles (225km) from the Afghan border.

Images show Iranian military officials inspecting the RQ-170 Sentinel stealth aircraft which appears to be undamaged.

US officials have acknowledged the loss of the unmanned plane, saying it had malfunctioned.

However, Iranian officials say its forces electronically hijacked the drone and steered it to the ground.

91Èȱ¬ security correspondent Frank Gardner says the intact condition of the Sentinel tends to support their claim.

Iran's Press TV said that the Iranian army's "electronic warfare unit" brought down the drone on 4 December as it was flying over the city of Kashmar.

Brig General Amir-Ali Hajizadeh, head of Iran's Revolutionary Guards' aerospace unit, told Iranian media that the drone "fell into the trap" of the unit "who then managed to land it with minimum damage".

He said Iran was "well aware of what priceless technological information" could be gleaned from the aircraft.

Nato said at the weekend that an unarmed reconnaissance aircraft had been flying a mission over western Afghanistan late last week when its operators lost control of it.

Pentagon officials have said they are concerned about Iran possibly acquiring information about the technology.

Iranian media said on Thursday that the foreign ministry had summoned the Swiss envoy to express its "strongest protest over the invasion of a US spy drone deep into its airspace".

Washington has no diplomatic relations with Iran and US affairs in the country are dealt with via the Swiss embassy in Tehran.

A statement said the ministry had asked for an immediate explanation and had demanded compensation from Washington.

A report in The New York Times on Thursday said the "stealth" drone had been part of a US surveillance programme mapping Iran's suspected nuclear sites.

The US and its allies suspect Iran of secretly trying to build a nuclear weapon - something Tehran strongly denies.

A recent report by the UN's nuclear watchdog said Iran had carried out tests "relevant to the development of a nuclear device".

Washington and Israel have not ruled out military action against Iran's nuclear facilities if sanctions and diplomacy fail.

Iran has vowed to respond by attacking Israeli and US interests in the region.