SPANISH Eurofighter jets have been suspended from Nato exercises in the Baltics after one of them accidentally fired an air-to-air missile over south-east Estonia.

The advanced medium-range air-to-air missile (AMRAAM) the fighter was carrying uses radar technology and carries a warhead.

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Although it has a built-in self-destruct mode designed to explode in the air, no explosion was heard when it was fired earlier this week 60 miles from the country’s border with Russia, near the city of Otepaa.

Estonian authorities think it may have hit the ground and are still searching for it.

Nato has delegated the interception of any unauthorised flights to French Mirage 2000 jets and Portuguese F-16 squadrons

The exercises test Nato responses to aircraft that approach allied airspace without following international flight regulations.

A statement from the Spanish Ministry of Defence confirmed that the missile had been fired accidentally by one of its fighters, but added: “The air-to-air missile has not hit any aircraft.

“The defence ministry has opened an investigation to clarify the exact cause of the incident.”

Military sources say an investigation is continuing, but they suspect that human error is the most likely cause, as they have found no errors in any of the software systems used.

However, it would be a very unusual mistake, given that the fighter was being flown by a highly experienced pilot who would have to go through a multi-stage procedure before being able to launch the missile.

Neither had the pilot assigned a target to the AMRAAM as it would probably have hit one of the other fighters that were also taking part in the exercise.

The National: epa05063308 NATO Secretary General Jens Stoltenberg answer media questions during a joint press conference after his meeting with Albanian Prime Minister Edi Rama, (not pictured) in Tirana, Albania, 10 December 2015. NATO Secretary General Jens Stoltenber

Nato Secretary-General Jens Stoltenberg

In a normal engagement a missile would be launched from about 20 miles, guided by its own navigation system, before its radar detected the target and guided the weapon to it.

Jüri Ratas, the Estonian prime minister, raised the issue in a phone call with Nato Secretary-General Jens Stoltenberg. Ratas said: “I told the secretary general of Nato that it is a serious incident and we are understandably concerned about this in Estonia.

“Thank God that as far as we know, no one was hurt as a result of the incident.”

A spokesperson for Nato said Stoltenberg offered the alliance’s full support for the investigation.

Spanish Defence Minister Margarita Robles also raised the incident with Jüri Luik, her Estonian counterpart.

Nato sources indicated that Estonia had remained “low-key” about the issue, because “everyone is aware that such an incident, while improbable, cannot be ruled out”.

Members of the alliance ensure the defence of the Baltic states’ airspace free of charge, as Estonia, Latvia and Lithuania have no fighter jets of their own.

Live weapons are said to be routinely carried on such Baltic air policing exercises.

Spain currently has more than 130 personnel and six Eurofighter EF-2000 jets from its Morón de la Frontera (Seville) base deployed in the Baltics – based at Siauliai in northern Lithuania.