The Russian Interfax news agency quoted an unidentified military source in Moscow as saying the 2007 contract, which reportedly involved at least two coastal-defense Bastion anti-ship systems with 72 Yakhonts, "was completely fulfilled, almost ahead of time."
The contract is worth an estimated $300 million.
Interfax noted that "this weapon allows coverage of the entire coastline of Syria from possible attacks from the sea."
It isn't known when the delivery was made. But Syria's acquisition of the Yakhont, which Russia calls the P-800, has caused considerable alarm in Israel.
The SS-N-26, with a range of 190 miles and a maximum speed of 1,900 miles an hour, carries a warhead of 440 pounds of high explosive, enough to sink a large warship.
The weapon's nearest U.S. counterparts, Raytheon's BGM-109 Tomahawk and Boeing's AGM-84 Harpoon, are subsonic. The best French equivalent, MBDA's MM-40 Exocet, only has a range of 45 miles.
The Russian delivery was carried out as Assad battles for survival against a 9-month-old uprising to topple his dictatorial regime in which his security forces have killed, by U.N. count, at least 4,000 people since mid-March.
While international pressure against the regime has steadily mounted as the bloodletting goes on, with some 950 people killed in November alone, Moscow has stood by its ally in Damascus.
Russian Foreign Minister Sergei Lavrov last week rejected U.N. calls for an arms embargo on Syria on charges of committing crimes against humanity. Lavrov said that a similar move against Libya had favored rebels opposed to Moammar Gadhafi, who toppled and killed him in a civil war.
Moscow has had close ties with Damascus and has been one of its main arms suppliers, as it was during the Soviet era. Syria is the largest buyer of Russian weapons in the Middle East. Moscow has arms contracts with Damascus worth at least $3 billion-$5 billion, the Russian RIA Novosti news agency reported.
The Yakhonts are likely to be deployed to protect a planned Russian naval base at the Syrian port of Tartous in the eastern Mediterranean. Russia has said it is sending the missile cruiser Admiral Kuznetsov and escort vessels to visit Tartous during an upcoming two-month Mediterranean tour.
That follows the deployment of the U.S. Navy's latest aircraft carrier, the USS George H.W. Bush, off the Syrian coast in recent days, and underlines Moscow's commitment to Syria.
The Tartous base, currently under construction by 600 Russian technicians, will be Russia's only military foothold in the region and has also caused consternation in Israel.
The Israelis say some of the Yakhonts could end up in the hands of Hezbollah, Iran's main proxy in Lebanon and a key Syrian ally.
While Middle East security experts say they doubt that, given the need to protect the Russians' base at Tartous, Syria has provided Hezbollah with thousands of missiles and rockets in recent years.
In the opening phase of the 2006 war between Hezbollah and Israel, the Shiite movement seriously damaged an Israeli corvette off the Lebanese coast with a Chinese-designed C-801 missile provided by Iran via Syria.
Israeli military sources reported Saturday the Syrians test-fired missiles in the northeastern part of the country, including a Scud-B ballistic missile.
The Israelis deduced that the tests, broadcast on Syria's state television, were intended as a demonstration of the embattled regime's strength rather than to intimidate Israel.
There has been growing talk of a Libya-style multinational intervention in Syria in a bid to end the bloodletting. The tests were likely to warn off countries contemplating such action.
On Monday, former Israeli Chief of Staff Shaul Mofaz, now chairman of the Knesset's Foreign Affairs and Defense Committee, warned that Assad could strike out at Israel if the pressure builds up on his regime.
"The closer the Assad regime in Syria gets to death's door, the greater the threat against Israel becomes," he declared.
"It can be reasonably assumed that in the twilight of his rule, Assad will try to deflect attention from the massacre of his own people by starting a conflict with Israel."