An Argentine submarine that disappeared with 44 crew members on board had been on a spying mission to the Falklands, the country's government has admitted.

Argentina's Navy has always claimed the ARA San Juan was carrying out training exercises when it vanished without a trace in November last year.

The sub has never been found but investigators claim a violent explosion was reported near its last known location in the South Atlantic, as it returned to the Mar del Plata naval base.

But now the government's chief of staff has admitted that the vessel had actually been ordered to the Falkland Islands - which the country calls Malvinas - to identify 'ships and aircraft'.

Argentine submarine ARA San Juan (pictured) that disappeared with 44 crew members on board had been on a spying mission to the Falklands, the country's government has admitted

Marcos Penas, answering a question arising from a report into the sub's disappearance, told Argentina's Congress that the San Juan's 'primary tactical objective' was 'the location, identification, photographic/film recording of refrigerated ships, logistic ships, oil tankers, and research vessels using other flags'.

But he added: 'Secondary material coming from this activity was to establish the identity of ships and aircraft operating from the Malvinas.'

Pena also revealed a list of the vessels and aircraft the submarine had identified, which included RAF planes and aircraft belonging to the Falkland Islands Government.

The admission backs up a leaked 'confidential' document about the submarine's activities which was passed on to Argentinian website Infobae last month.

Dated October 24 last year - a month before the vessel disappeared - and entitled 'Control of the Sea Patrol', the Navy document details what would be the ARA San Juan's mission.

The submarine's disappearance triggered an international search for the ship and crew members, who have been presumed dead for weeks. Pictured above is the last known image of the submarine

The submarine is ordered to 'obtain the identification by means of photographic images or video of the vessels of interested in the said area and register their activity.

The list of targets includes cargo ships and oil tankers but also 'RAF130 aircraft and Malvinas Government Aircraft'.

According to the timetable set out in the document, in what is described as 'Phase II of Stage 4', on November 15 - the day the sub disappeared - it was to proceed to an area called 'Milagros' and carry out an 'underwater attack' exercise.

The revelations have come after family members of missing crew members claimed the submarine was being 'chased by a British helicopter' when it went missing.

This claim was dismissed at the time as 'completely untrue' by Britain's Ministry of Defence.

One of the missing sailors, Roberto Daniel Medina, reportedly told her sister Jesica Medina days before the vessel's last communication that that the ARA San Juan submarine had travelled close to the Falkland Islands, and that a Royal Navy helicopter was trying to track them.

Jesica said the sub sailed close to the Falkands on November 3, alerting the British Navy which began searching for the vessel.

Second sub-officer Roberto told her they were now heading for home, writing: 'On Monday an English helicopter was looking for us, and yesterday the Chileans, there has been a lot going on.'

She said: 'It was a strange message in which he told us a British helicopter and a Chilean ship had been chasing them.

'I don't know why he said it. but unfortunately we didn't continue with that conversation, we started talking about other things, the kids, the family, and it stayed like that. It was his last message.'

The missing crew of ARA San Juan Lieutenant Eliana Maria Krawczyk, 35, is third-in-command of the sub. As chief weapons officer, she is responsible for the ship's arsenal of 22 torpedoes. She grew up in Misiones province, near the borders with Paraguay and Brazil, around 1,000 kilometers (600 miles) from the sea. She dreamed of becoming an engineer but enrolled at naval school after a double family tragedy - her brother's death in a car accident and her mother dying from a heart attack. She enrolled in the naval school instead, having her first encounter with the sea at 21. She specialized in under-sea warfare, becoming Latin America's first submarine officer. Captain Pedro Martin Fernandez has been commander of the San Juan since 2015. Married with three adolescent children he flirted with the idea of becoming a teacher before joining the navy. In two decades of missions and training programs he has traveled the world. The 45-year-old lived for a decade in Mar del Plata, home port of the navy's two operational submarines, the San Juan and the Salta. Luis Niz (left) only joined the crew of the San Juan recently, after getting a promotion in 2016 Photographs of the crew of Argentina's lost submarine have emerged for the first time, including that of Captain Pedro Martin Fernandez (pictured right) Maria Leguizamon, whose husband German Suarez (pictured) is among the missing, told how 40 relatives gathered at the naval base were told about the explosion minutes before the press conference in Buenos Aires Luis Niz, 25, was due to marry soldier Alejandra Morales on December 7. He only joined the crew of the San Juan after getting a promotion in 2016. Lieutenant Renzo Martin Silva, 32, has been in the navy since the age of 18. The submarine enthusiast grew up in the foothills of the Andes in the Argentine province of San Juan, for which the submarine was named. He planned to marry his girlfriend, a soldier, Lieutenant Maria Eugenia Ulivarri Rodi, next year. Mario Armando Toconas Oriundo, 36, has spent 13 years in the navy. From Patagonia, he went to live in Mar del Plata, a seaside resort as well as the sub's home port. Father of an eight-year-old boy, his partner is four months pregnant with their second child. Fernando Santilli, 35, became a submariner seven years ago. He left the wine-growing province of Mendoza to become an engineer. His wife, Jessica Gopar, posted a moving letter on Facebook on Tuesday, in which she said every day of waiting 'is a little harder. There are moments of hope, others of great distress. You cannot imagine how many people are praying for you.' She dedicated a few lines of her note to the commander, asking him to 'do the impossible and get back to the surface. You have 44 lives in your hands. I'm waiting for my love. See you soon.' Fernando Santilli (right) left the wine-growing province of Mendoza to become an engineer Lieutenant Renzo Martin Silva, 32, planned to marry his girlfriend, a soldier, Lieutenant Maria Eugenia Ulivarri Rodi, next year Advertisement

Jesica told Argentina's La Gaceta newspaper that 'many' other families of other missing crew members also received reports from their loved ones that they had been fleeing a British helicopter at the time of their disappearance.

She added: 'I don't know how close they got to the Malvinas (Falklands), and I don't know what the political situation is like. That's what he told us and that is what we were left with.'

According to the Argentine Navy, the vessel last made contact with commanders to report that water had entered the vessel through its snorkel and caused a battery fault.

Experts said the crew only had up to 10 days of oxygen if the sub remained intact under the sea, but despite a frantic international search, including Britain's HMS Protector and the Royal Navy's elite submarine rescue team.

Families later accused the Argentinian government of a cover-up after they were forced to confirm information that there had been a violent explosion in the area where the vessel would have been, just hours after its last transmission.

The explosion is believed to have happened between 100 and 1000 metres under the water and sent the submarine plumetting to more than 3,000 metres.