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