MOSCOW: Russia has loaded its only aircraft carrier with supersonic jets and anti-ship helicopters in preparation for a rare port call to Syria before the end of the year, military officials said on Tuesday.

The Admiral Kuznetsov will lead Russia's first major flotilla to Syria since 2008 after completing final preparations at its Norther Fleet base near the city of Murmansk, the official said.

The mission will include Russia's newest anti-submarine destroyer and a fleet of smaller ships that will ferry supplies between the heavy aircraft carrier and the shore once it enters Syria's Tartus port harbour.

The Izvestia daily had on Monday reported that the naval mission to Russia's close Arab world ally would take place in the spring of 2012.

But Russian news reports moved that date ahead by several months on Tuesday despite officials' continued refusal to link the operation to the escalating tensions around strongman Bashar al-Assad's crackdown on street protests.

"Our ships' visit to Syria was planned in advance and has no relation to the current events in Syria," the ITAR-TASS news agency quoted an unnamed Russian defence official as saying.

"This is a matter of improving the training of our naval crew," the official said.

Syria's ambassador to Russia echoed the statement.

"You cannot link the Russian ships' plans to enter Tartus to the current situation in Syria," ambassador Suleiman Abu Diyab told the Interfax news agency.

"Syria is Russia's friend and your ships can enter our port for repairs or any other reason," the Damascus envoy said.

The Tartus port was designed to enable Soviet ships to conduct quick repairs on missions to the Mediterranean and neighbouring seas.

Russia's top general declined to confirm the port call, saying only that a series of excercies in the region were planned.

"We have scheduled a series of exercises, but these are not linked to Syria," chief of staff Nikolai Makarov told reporters without providing further details.

Syria turned into one of Russia's most important Arab world allies after the fall of Moamer Kadhafi in Libya earlier this year.

It remains a key military client state with outstanding defence contracts worth several billion dollars and also provides Russia with diplomatic leverage in the stalled Middle East peace process.

Russia has flatly refused to tear up its defence contracts with Assad despite growing pressure from the US administration and has already vetoed a draft UN resolution that threatened tough sanctions against the regime.

Foreign Minister Sergei Lavrov reaffirmed Russia's tough stance by urging both Washington and the European Union to stop presenting "ultimatums".

He also levelled criticism at a United Nations monitors' report that on Monday identified a series of grave violations by Assad's forces that included torture and the murder of children

"Armed people are treating civilians very severely," Russia's top diplomat said.

"But recently, more and more often, this concerns not so much the actions of the authorities, but of the armed groups that provoke disorder."