June 12 (UPI) -- The French Navy on Friday announced the test of a submarine-launched ballistic missile on Friday by the last submarine in its fleet to receive a missile upgrade.
The missile crossed the Atlantic Ocean, striking an area at sea nearly 400 miles east of Puerto Rico, officials said.
"This test was carried out without nuclear warhead and in strict compliance with France's international commitments," an official statement on Friday said. "This firing validates the operational capacity of the SSBN Le Téméraire's global weapon system and once again demonstrates the high-tech excellence that French industries are implementing in this area."
The launch, from the submarine Le Temeraire in Audierne Bay, off the coast of Brittany near western France, was conducted in relative secrecy. Congratulations later were announced by French Defense Secretary Florence Parly and French Navy Chief of Staff Adm. Christophe Prazuck.
The submarine is one of four in the French Navy with the "SSBN" classification, indicating the capability of firing nuclear ballistic missiles underwater.
It is fitted with 16 launching tubes and French-made M51 missiles, as well as traditional armaments. Three of the four submarines, including the Le Temeraire, were retrofitted with the missile capability.
Each missile can carry up to 10 independently targetable TN 75 thermonuclear warheads, although none were used in the test.
Some observers speculated that the test Friday used an advanced version of the missile, the M51 Mk. 3, currently under development. The test also served to underscore France's formidable second-strike nuclear capability.
At least one French SSBN submarine is kept on alert at any time, according to officials.