Despite formally denying any strife between their CEOs, the two companies have often clashed over issues such as oil transportation fees and Rosneft's rising oil exports to China. Sechin, 58, has been close to President Vladimir Putin for two decades, while Tokarev, 68, is also a long-time ally. Putin, Tokarev and Sechin all worked in the city administration for St Petersburg in the 1990s after the collapse of the Soviet Union. When asked to comment on the row, Kremlin spokesman Dmitry Peskov told reporters on a daily conference call that it was a "corporate matter". Transneft transports 83% of Russian oil via its network, while Rosneft accounts for over 40% of Russian output. An industry source said oil output at Yuganskneftegaz in West Siberia fell 30% during July 1-8 compared with the June average.