MAR DEL PLATA, Argentina - A multinational armada of aircraft and vessels battled high winds and raging seas on Sunday as they intensified their search for a missing Argentine submarine, after apparent attempted distress calls raised hopes the 44 crew members may still be alive.

There has been no contact with the ARA San Juan, a German-built diesel-electric sub, since early on Wednesday.

An air and sea search is under way with help from countries including Brazil, Britain, Chile, the United States and Uruguay.

The search will continue "until it appears," the Argentine Navy said.

"We will continue to redouble our efforts tomorrow, day and night, looking by air, sea and underwater until the submarine appears," said captain Gabriel Galeazzi, spokesman for the Navy.

Hopes of finding survivors were revived when the Navy said on Saturday that its bases had received seven satellite calls attributed to the submersible.

However, the Navy was unable to confirm that those calls originated from the submarine.

The TR-1700 class submarine had been returning from a routine mission to Ushuaia, near the southernmost tip of South America, to its base at Mar del Plata.

It is one of three submarines in the Argentine fleet. Sixty-five meters long and seven meters wide, it was built by Germany's Thyssen Nordseewerke and launched in 1983.

Seven-meter waves

The calls revived hopes that the submarine has surfaced, but a powerful storm that has whipped up waves reaching 7 meters in height has made geolocation difficult, officials said.

Balbi said weather conditions were not expected to improve before Tuesday.

Despite the bad weather,"10 aircraft, both domestic and foreign, are in a search rotation 24 hours a day, each in a different area", he said.

He said the attempt to use a satellite phone indicates that "the submarine had to emerge to a depth that allowed the call".

The last regular communication with the San Juan was early on Wednesday, when the submarine was 430 kilometers off Argentina's coast in the Gulf of San Jorge.

Rescuers are focusing on an ocean patch about 300 km in diameter, radiating from the last point of contact.

Relatives of crew members unfurled a flag at the naval base that read: "Be strong Argentina. We trust in God, We wait for you."