RUSSIA has for the first time explained the presence of a fleet of warships off north-eastern Australia, saying that the ships are testing their range capability, in case they have to do climate change research in the Antarctic.

The Russian embassy also said the fleet could, if necessary, provide security for Russian President Vladimir Putin, who arrives in Brisbane for the G20 tonight.

The four Russian warships are conducting exercises in international waters around the Coral Sea in a move that has been interpreted as a show of force by Mr Putin.

Moscow’s explanation comes as Defence said a third Australian naval ship has been deployed to monitor the fleet, with a fourth nearby.

A government source said the Australian warship HMAS Parramatta is conducting “exercises” with the Russian cruiser Varyag, as the powerful Russian warship steams towards Brisbane.

The flagship of the Russian Pacific Fleet separated from her three support vessels yesterday and headed closer to the Queensland coast.

By this morning she was off the Sunshine Coast and remaining in international waters.

The frigate HMAS Paramatta contacted the huge Russian warship by radio and conducted a so-called “commex” or communications exercise with the vessel.

This includes testing all forms of maritime communications including radios, signal flags and semaphore lights.

“The Russians have responded happily to the exercise,” a government source said.

A second frigate, HMAS Stuart, remains in a holding pattern off Moreton Bay where she will be joined by the replenishment ship HMAS Sirius for refuelling.

According to Defence sources, a third frigate, HMAS Sydney, probably won’t be diverted from her home port of Sydney following an exercise in New Zealand.

“Everyone is talking so we are unlikely to send another ship north now,” the source said.

The three other Russian ships have headed east into the Pacific Ocean and are no longer being monitored by Australian ships or RAAF Orion Maritime Patrol aircraft.

Officials expect the Varyag to remain in international waters off Brisbane until the G-20 summit concludes and Russian resident Vladimir Putin leaves Brisbane when she is is likely to join her support fleet in the eastern Pacific.

Both Parramatta and Stuart are understood to be carrying Seahawk anti-submarine warfare helicopters, although defence sources said it was unlikely that a Russian submarine is in the area.

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News Corp Australia understands that the government also asked the Navy about the possibility of a Collins Class submarine joining the mission but was told that the nearest boat was in Perth and would not be able to reach the area until well after the G20 summit was over.

Three RAAF AP-3C Orion maritime surveillance aircraft, also equipped for anti-submarine warfare, have been sent to Amberley near Brisbane and are maintaining a 24/7 patrol above the flotilla, according to official sources.

The Russian task group is steaming southwest in the Coral Sea off Townsville at 15 knots and is due to arrive in international waters off the G20 venue on Saturday, November 15. The ships will be off Rockhampton on Friday.

While Australian officials have played down the presence of the flotilla led by the Russian Pacific Fleet flagship the cruiser Varyag, frantic efforts have been underway in Moscow to establish the intention of the fleet, according to a government source.

It is understood that the Australian Defence Attache in the Russian capital has advised senior Russian military officers that the ships would be refused port access in Brisbane unless there was an emergency.

The National Security Committee of Cabinet is not scheduled to meet ahead of the weekend G20 conference but according to insiders the lines have been “running hot”.

Prime Minister Tony Abbott threatened to “shirt-front” Mr Putin over Russia’s role in the downing of Malaysia Airlines flight MH17 and the deaths of 38 Australian residents.

The unpredictable Russian strongman will arrive in Brisbane for the summit on Friday and is expecting a hostile reception.

Military fellow at the Lowy Institute James Brown said it made sense to have Russian warships nearby.

“If something did happen it helps to have military forces in the region,” Mr Brown said.

Defence released a statement saying that Russian warships had been deployed to previous international summits including the 2009 APEC meeting in Singapore and the visit of President Medvedev to San Francisco in 2010.

Russian has increased its global military activity in recent weeks with submarine incursions in the Baltic, bomber flights over the Arctic and the Caribbean and the task group in the South Pacific.

Swedish Navy submarine Captain Jens Nykvist told a Submarine Institute conference in Fremantle yesterday that the Baltic had returned to “Cold War” status after years of peace.

“We have increased activities and it has affected our operations ... we spend more time at sea. It is an interesting future we see,” Captain Nykvist said.

The Defence Department confirmed the ship and aircraft deployments on Thursday night.

Additional reporting AAP