BEIJING, Oct 25 (Reuters) - London copper prices fell for a third straight session on Thursday, hitting a two-week low as the metal considered to be an economic bellwether tracked a slump in global equity markets. Copper has been losing ground on concerns of a slowdown in top metals consumer China, which pledged to support illiquid private companies after third-quarter GDP growth slowed to 6.5 percent, the lowest since 2009. "Macro headlines have been unhelpful, and commentary from some industrial companies about weaker Chinese demand is adding fuel to the fire," Jefferies analyst Christopher LaFemina wrote in a note. Import premiums in China SMM-CUYP-CN have fallen to $112.50 per tonne, the lowest since Sept. 19, after hitting three-year highs of $120 a tonne late last month. FUNDAMENTALS * LME COPPER: Three-month copper on the London Metal Exchange slipped as much a 1 percent to $6,115 a tonne, the lowest since Oct. 11, and was down 0.7 percent at $6,138.50 a tonne as of 0451 GMT. * SHFE COPPER: The most-traded December copper contract on the Shanghai Futures Exchange was also down for a third day, falling as much as 1.5 percent to 49,360 yuan ($7,109.73) a tonne, its weakest since Sept. 21, before trimming losses to 0.8 percent by the mid-session interval. * OTHER METALS: Shanghai nickel slumped as much as 2.8 percent to 100,160 yuan a tonne, the lowest since Sept. 12, before cutting losses to 1.1 percent, while lead and aluminium moved higher after drops in LME stocks on Wednesday. * COPPER: Freeport-McMoRan Inc on Wednesday reported market-beating results as output and grades at its big Indonesian mine rose, but early share gains turned negative as investors digested forecasts for the world's biggest public copper miner.