MOSCOW, July 20 (Reuters) - Russia views Taliban gains in northern Afghanistan as having a security upside because the group is hostile to what Moscow regards as more dangerous Islamist extremists, a senior Russian diplomat said on Tuesday, according to the Interfax news agency. Taliban fighters have made major advances as U.S. forces pull out after 20 years of war, a security headache for Moscow which fears refugees may be pushed into its Central Asian backyard and destabilise its southern defensive flank. read more But Zamir Kabulov, President Vladimir Putin"s special representative on Afghanistan, was cited by Interfax on Tuesday as saying the Taliban"s progress in northern Afghanistan also had security advantages for Russia"s allies in Central Asia like Tajikistan and Uzbekistan. Russia has expressed alarm over what it has described as the growing strength of Islamic State elements in northern Afghanistan, and Kabulov was quoted as saying the Taliban would at least try to take on and defeat those elements. "The fact that the Taliban are taking control of districts (in the north) has a positive aspect to it. Why? Because most of these (extremist) groups are not focused on domestic matters, but on Central Asia, Pakistan or Iran," Interfax cited Kabulov as telling an event organised by the Valdai discussion club. "The Talibs, who are taking these districts over, are their sworn enemies, and unlike the Afghan government not to mention the Anglo-Saxons...the Talibs fight and destroy them," he was cited as saying. Kabulov was also quoted as saying that Russia had so far not seen any evidence that the Taliban had tried to cross the border into Tajikistan or Uzbekistan.