Iran has vowed to defend its borders after shooting down a US drone it said entered the country’s airspace, as Donald Trump revealed he called off retaliatory airstrikes against Iranian targets with just minutes to spare.

The downing of the drone has seen tensions soar between the bitter rivals, after a series of attacks on tankers in the strategically important Strait of Hormuz.

Washington insists its $120m (£94m) Global Hawk drone, one of the most expensive pieces of military equipment in the country’s arsenal, was 34km from Iran when it was destroyed by a surface-to-air missile in an “unprovoked attack”.

However, Iran’s deputy foreign minister Abbas Araghchi said on Friday that he handed “indisputable” evidence to the Swiss ambassador to Iran, whose country represents US interests for Iran, that the drone had violated Iranian airspace.

Iranian television broadcast images of what it said was “debris” of the downed drone recovered from Iran’s territorial waters.

Tensions high as Trump approves new Iran sanctions: In pictures Show all 17 1 /17 Tensions high as Trump approves new Iran sanctions: In pictures Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, their surface-to-air missile is seen as it shoots down a US surveillance drone EPA Tensions high as Trump approves new Iran sanctions: In pictures This photo shows US RQ-4A Global Hawk unmanned surveillance drone. A drone of this model was shot down by Iran on Thursday 21 June AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures An oil tanker is on fire after it was subject to a suspected attacked at the Gulf of Oman on June 13. The US has blamed Iran for the attack Reuters Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, debris from the downed US drone is seen after it was recovered from Iranian waters AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures US President Trump holds up a signed executive order to increase sanctions on Iran on 24 June AP Tensions high as Trump approves new Iran sanctions: In pictures Iranian President Rouhani stated in a televised address that the White House is "afflicted by mental retardation" following the increase in sanctions on 25 June EPA Tensions high as Trump approves new Iran sanctions: In pictures An Iranian navy boat tackles the fire on the Norwegian owned Front Altair oil tanker after it was hit in a suspected attack AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, debris from the downed US drone is seen after it was recovered from Iranian waters AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures A screenshot from a video released by the US Department of Defense that the US claims to show Iranian removing an unexploded limpet mine form the hull of the Japan-owned ship that was attacked in the Gulf of Oman on June 13 Getty Tensions high as Trump approves new Iran sanctions: In pictures An item reportedly found on the Japan-owned oil tanker that was attacked on June 13 in the Gulf of Oman AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures A handout photograph from the US Department of Defense shows a composite material that the US claim was left behind on the hull of the Japan-owned oil tanker following the removal of an unexploded limpet mine Getty Tensions high as Trump approves new Iran sanctions: In pictures A view from the cabin of an Iranian navy boat as it tackles the fire on the Norwegian owned Front Altair oil tanker after it was hit in a suspected attack EPA Tensions high as Trump approves new Iran sanctions: In pictures Release by US government A picture released by U.S. Central Command shows damage to the hull of the oil tanker Kokuka Courageous. The picture suggests that the ship is 'likely' to have been hit by a mine as the US Secretary of State Mike Pompeo moves to blame Iran for the suspected attack Reuters Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures Release by US government A picture released by U.S. Central Command shows damage to the hull of the oil tanker Kokuka Courageous. The pictures suggests that the ship is 'likely' to have been hit by a mine as the US Secretary of State Mike Pompeo moves to blame Iran for the suspected attack EPA

“The Islamic Republic of Iran would not hesitate for a moment to decisively defend its territory against any aggression,” Mr Araghchi added.

Amirali Hajizadeh, the commander of the aerospace arm of Iran’s elite Revolutionary Guards, meanwhile claimed the drone was warned twice before it was hit. He added that Iranian forces had refrained from targeting a nearby US plane which had 35 people on board.

“With the US drone in the region there was also an American P-8 plane with 35 people on board,” Mr Hajizadeh was quoted as saying by Iran’s Tasnim news agency.

“This plane also entered our airspace and we could have shot it down, but we did not.”

Mr Trump confirmed that the US had nearly struck Iranian targets shortly after the drone was taken out, saying just 10 minutes before the retaliatory strikes were due to be carried out that he pulled back, due to concern over the death toll.

“I asked, how many will die. 150 people, sir, was the answer from a General,” the president tweeted, concluding it would not have been “proportionate to shooting down an unmanned drone”.

Iran military releases footage of 'missile strike on US drone'

“I am in no hurry, our Military is rebuilt, new, and ready to go,” he wrote.

The shoot-down came as Iran was already accused by Washington of carrying out attacks on tankers in the congested shipping lanes heading out of the Gulf through the Strait of Hormuz.

Fearing an escalation in the conflict, the US Federal Aviation Administration barred American civilian aircraft from flying over the waterway, warning of imminent danger from surface-to-air missiles.

Airlines from across the world swiftly followed suit. British Airways, KLM, Lufthansa and Qantas all altered their flight paths to avoid the area.

Pressure has steadily built since Mr Trump announced last year he was reimposing sanctions on Iran and pulling out of a 2015 nuclear deal between Iran and six world powers which aims to curtail Tehran’s nuclear ambitions.