"We feel anguish. We are reserved but will not lose our hope that they will return," Marcela Moyano, wife of machinist Hernan Rodriguez, told television network TN.

'We're very worried, we have little news, we're waiting for communication,' said Eduardo Krawczyk, father of weapons officer Eliana Krawczyk, 35.

"We can make up a thousand movies with happy and sad endings, but the reality is that the days pass by and not knowing anything kills you," Carlos Mendoza, the brother of submarine officer Fernando Ariel Mendoza said.

"Every minute is oxygen that's worth gold."

Many are also taking to social media to express their worries as the search continued into a second week, including Sofi Álvarez, 21, whose brother Luis Niz, 25, is on the ARA San Juan.

She tweeted: "We are here, all united, awaiting your arrival, 44 families and a very long wait. Do not stop asking, please, do not lose faith, hope. We are not going to stop until we hug them again.

"It does not matter what god you believe in, or what you believe, I only ask that with a prayer, good vibes, good energies ask for the alive appearance of the crew of the Argentine submarine ARA San Juan, one of them my eldest brother. I'm destroyed."

Speaking to MailOnline, she added: "We always talk to him before he leaves port and he did not give us any indication of a breakdown, on the contrary, he told me that in a few days we would see each other.

"He is about to get married in a few weeks."

From the Vatican, Argentine Pope Francis said he was making "fervent prayers" for the crew, and prayers have also come from legendary footballer Diego Maradona.

"I want to send strength and hope to all the relatives of the crew of the ARA San Juan submarine,' Maradona wrote on his official Instagram account.

"I think it's great that we are receiving help from other countries with better technology. And, although I wonder about those responsible for this situation, I think that today the most important thing is to rescue our boys."

This comes after one of the crew members reportedly warned her family that there had been issues on board, just days before it vanished.

Ms Krawczyk's brother has since revealed that she called the family before they set off and told them there was a mechanical problem.

Speaking to Argentine radio and newspapers, Roberto Krawczyk has said his sister told him that the submarine had needed repairs while in port.

ARA San Juan was returning to its base in Mar del Plata after a routine mission, and left Ushuaia last Monday. Authorities lost contact with the vessel two days later.

Navy spokesman Balbi said that if the sub was settled on the surface, or able to put up a snorkel to draw fresh air, there are supplies on board to last for a month.

But if the sub is underwater - as seems to be the case after surface searches failed to find it - then there is only enough air inside to last for a week.

The craft has already been missing for seven days, and search areas indicate it is likely in deep water, meaning sending up a snorkel would be problematic.

The last known communications from the sub's crew were on Wednesday last week. One call reported a routine battery fault, while the details of the second call have not been disclosed by the navy.

Storms, seen in this video, have complicated efforts to find the navy submarine, which had gone missing in the South Atlantic.

Authorities have mainly been scanning the sea from above, as storms have made the search difficult for boats.

The Royal Navy has deployed an ice patrol ship to help search for the missing submarine.

Britain sent the HSM Protector, a polar exploration vessel, to the southern Argentine Sea to assist in searches.

Britain and Argentina fought a war in 1982 over the Falklands Islands, which are called the Malvinas in Argentina.