* Russia detects ballistic launches in Mediterranean
* Israel carried out joint missile test with United States
* No missile strike reported on Syrian capital Damascus
* Markets nervous as US preparing possible Syria air strike (Adds Israeli missile test)
By Steve Gutterman
MOSCOW, Sept 3 (Reuters) - Russia raised the alarm on Tuesday after detecting the launch of two ballistic "objects" in the Mediterranean Sea but Israel later said it had carried out a joint missile test with the United States.
There were no reports of missile strikes on Syria. Syrian state sources said the missiles had fallen harmlessly into the sea and there were no explosions in the capital Damascus, Russian news agencies reported.
Initial reports of the launch by Russian news agencies had ruffled financial markets because the United States is preparing for a possible military strike on Syria over what it says was a chemical weapons attack by government forces in their conflict with rebels trying to overthrow President Bashar al-Assad.
But the Israeli Defence Ministry said it had tested a missile used as a target in a U.S.-funded anti-missile system at 9:15 a.m (0615 GMT), about the same time as the Russian radar picked up the launch.
"The trajectory of these objects goes from the central part of the Mediterranean Sea toward the eastern part of the Mediterranean coast," Russia's Interfax news agency quoted a Defence Ministry spokesman as saying.
The spokesman said the launch was picked up by an early warning radar station at Armavir, near the Black Sea, which is designed to detect missiles from Europe and Iran.
He did not say who had carried out the launch and whether any impact had been detected, but RIA news agency later quoted a source in Syria's "state structures" as saying the objects had fallen harmlessly into the sea.
The Russian Defence Ministry declined comment to Reuters.
The Russian Embassy in Syria said there were no signs of a missile attack or explosions in Damascus, state-run Itar-Tass reported.
Syria's early warning radar system did not detect any missiles landing on Syrian territory, according to a Syrian security source quoted by Lebanon's al-Manar television.
Russian Defence Minister Sergei Shoigu informed President Vladimir Putin of the launch but it was not immediately clear how he reacted.
Brent crude oil extended gains to rise by more than $1 per barrel and Dubai's share index fell after Russia said it detected the launches.
Russia opposes any outside military intervention in the Syrian civil war, and a Defence Ministry official had earlier criticised the United States for deploying warships in the Mediterranean close to Syria.
Assad's government denies responsibility for the deaths of hundreds of people in the alleged poison gas attack on Aug. 21.
Russia, Assad's most powerful backer during the more than two-year-old conflict in Syria, says it suspects the attack was staged by rebels to provoke military intervention and is critical of U.S. naval deployments in the Mediterranean.
Five U.S. destroyers and an amphibious ship are in the Mediterranean, poised for possible strikes against Syria with cruise missiles - which are not ballistic. U.S. officials said the aircraft carrier USS Nimitz and four other ships in its strike group moved into the Red Sea on Monday.
"The pressure being applied by the United States causes particular concern," Itar-Tass quoted Russian Defence Ministry official Oleg Dogayev as saying.
He said "the dispatch of ships armed with cruise missiles toward Syria's shores has a negative effect on the situation in the region." (Writing by Steve Gutterman, Editing by Timothy Heritage/Mark Heinrich)