Israel fired a missile in the Mediterranean to test a new defence system - but did not inform anyone beforehand.
The Tuesday morning launch - a joint exercise with the United States - was first reported by Russia, which said two "objects" following a ballistic trajectory had been fired from the Mediterranean.
Israel's Defence Ministry later said that it, along with a team of United States military advisers, had carried out a test-launch of a Sparrow missile.
The Sparrow, which simulates the long-range missiles of Syria and Iran, is used for target practice by Israel's US-backed anti-missile system, Arrow.
The test comes as the West debates whether to launch military strikes against the Syrian regime of Bashar al-Assad following its alleged use of chemical weapons last month.
"Israel routinely fires missiles or drones off its shores to test its own ballistic defence capabilities," a US official said in Washington.
Israeli Prime Minister Benjamin Netanyahu said the anti-missile system was a national "wall of iron". "These things give us the power to protect ourselves, and anyone who considers harming us would do best not to," he said in a speech.
Arrow designer Uzi Rabin said tests of the anti-missile system are planned "long, long in advance" and generally go unnoticed. "What apparently made the difference today is the high state of tension over Syria and Russia's unusual vigilance," he told Reuters.
Al Jazeera's Paul Brennan, reporting from Jerusalem on Tuesday, said it was "highly unusual that Israel should be involved in this joint exercise, as it could draw Israel into the conflict," he said.