By Sylvia Westall and Dominic Evans
BEIRUT (Reuters) - Syrian troops and militia backed by Russian jets mounted what appeared to be their first major coordinated assaults on Syrian insurgents on Wednesday and Moscow said its warships fired a barrage of missiles at them from the Caspian Sea, a sign of its new military reach.
The combined assault hit towns close to the main north-south highway that runs through major cities in the mainly government-held west of Syria, said the Syrian Observatory for Human Rights, a British-based group which tracks the conflict via a network of sources within the country.
Ground attacks by Syrian government forces and their militia allies using heavy surface-to-surface missile bombardments hit at least four insurgent positions and there were heavy clashes, the head of the Observatory, Rami Abdulrahman, said.
The Iranian-backed Hezbollah militia took part in the fighting, a regional source said.
Islamic State militants have seized much of Syria since civil war grew out of anti-government protests in 2011, but the areas targeted in Wednesday's combined assault are held by other rebels, some U.S.-backed, fuelling allegations by Russia's critics that its real aim is to help the government.
Moscow says it shares the West's aim of preventing the spread of Islamic State, and Russian Defense Minister Sergei Shoigu told President Vladimir Putin during a televised meeting that four Russian warships in the Caspian Sea had launched 26 missiles at Islamic State in Syria earlier in the day.
The missiles would have passed over Iran and Iraq to reach their targets, covering what Shoigu described as a distance of almost 1,500 km (900 miles), the latest display of Russian military power at a time when relations with the West are at a post-Cold War low over Ukraine.
The terrain-hugging Kalibr cruise missiles, known by NATO by the codename Sizzler, fly at an altitude of 50 meters and are accurate to within three meters, the Russian defense ministry said.
The air campaign in Syria has caught Washington and its allies on the back foot and alarmed Syria's northern neighbor Turkey, which says its airspace has been repeatedly violated by Russian jets.
Ankara summoned Russia's ambassador for the third time in four days over the reported violations, which NATO has said appeared to be deliberate and were "extremely dangerous".
Turkey said Syria-based missile systems harassed its warplanes on Tuesday while eight F-16 jets were on a patrol flight along the Syria border.
IRAQ LOOKS TO RUSSIA
Syrian state television quoted a military source as saying the missiles fired by Russian ships targeted 11 Islamic State positions in Raqqa, Aleppo and Idlib.
The missiles destroyed bomb-making factories, command posts, weapons and ammunition and fuel depots, as well as "terrorist training centers", the TV said.
Russian air strikes destroyed the main weapons depots of a U.S.-trained rebel group, the Liwa Suqour al-Jabal, their commander said.
In conversation with Shoigu, Putin said it was too early to talk about the results of Russia's operations in Syria and ordered his minister to continue cooperation with the United States, Turkey, Saudi Arabia, Iran and Iraq on the crisis.
However, U.S. Defense Secretary Ash Carter said the United States would not cooperate militarily with Russia in Syria, although it was willing to hold discussions to secure the safety of its own pilots bombing IS targets in Syria.
Calling Moscow's strategy "tragically flawed", he renewed accusations that the strikes were not focused on Islamic State. The Russian defense ministry accused the U.S. air force of not always bombing Islamic State targets itself.
Turkish Prime Minister Ahmet Davutoglu said only two of 57 Russian air strikes in Syria so far had hit Islamic State, while the rest had been against the moderate opposition, the only forces fighting the hard-line insurgents in northwestern Syria.
But in Iraq, the head of parliament's defense and security committee said Baghdad may request Russian air strikes against Islamic State on its soil soon and wants Moscow to have a bigger role than Washington in fighting the group.
Iraq's government and powerful Iranian-backed Shi'ite militias question the United States' resolve in fighting Islamic State militants, who control a third of the country, saying U.S.-led coalition air strikes are ineffective.
“We might be forced to ask Russia to launch air strikes in Iraq soon ... and that depends on their success in Syria," Hakim al-Zamili told Reuters.
AIR SUPPORT ONLY SO FAR
Russia's military build-up in Syria included a growing naval presence, long-range rockets and a battalion of troops backed by Moscow's most modern tanks, the U.S. ambassador to NATO said.
"There is a considerable and growing Russia naval presence in the eastern Mediterranean, more than 10 ships now, which is a bit out of the ordinary," Douglas Lute told reporters ahead of a meeting of alliance defense ministers in Brussels.
Abdulrahman said Russia appeared to have stuck to air support on Wednesday. The assault followed a report by Reuters last week that allies of Syrian President Bashar al-Assad, including Iranians, were preparing to recapture territory lost by the government to rebels in rapid advances this year.
"There is no information yet of any (government) advances on the ground, but the air strikes have hit vehicles and insurgent bases," Abdulrahman said.
The regional source, who is familiar with the military situation in Syria, said forces including Hezbollah fighters were taking part in the ground attack against four rebel-held areas in western Syria.
Hezbollah-run al-Manar television said in a newsflash that "an operation by the Syrian army started in a number of villages and towns in the northern countryside of Hama province".
A video posted by the media office of an opposition group in Hama province on YouTube purported to show heavy rocket strikes by pro-government forces on Wednesday hitting an areas in the northern Hama countryside.
Other footage from Hama showed rebels from the Free Syrian Army firing anti-tank missiles and hitting two army tanks.
(Additional reporting by Laila Bassam in BEIRUT, Alexander Winning in MOSCOW, Phil Stewart and Crispian Balmer in ROME and Michael Georgy in BAGHDAD; writing by Philippa Fletcher,; editing by Peter Millership and Giles Elgood)