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. 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. Additional reporting AAP