* Rebar, iron ore futures drop more than 3 pct
* Coking coal tumbles 6.4 pct, coke down 7 pct
* China steel output slips from record as smog war bites (Updates prices)
By Manolo Serapio Jr
MANILA, Oct 19 (Reuters) - Prices of steelmaking commodities iron ore and coking coal fell sharply on Thursday, pressured by worries over slower demand as Chinese mills curb output in line with Beijing's campaign to fight smog.
Iron ore futures slid more than 3 percent and coking coal dropped more than 6 percent. Rebar steel futures tumbled over 3 percent after data showed China's steel output rose year-on-year in September, though below the monthly record reached in August.
Mills in the northern part of China are expected to cut output by up to half during winter, from Nov. 15 to March 15, on government orders to limit pollution. Some cities, however, have already implemented the steel output curbs, including the top steelmaking city of Tangshan. most-traded iron ore contract for January delivery on the Dalian Commodity Exchange DCIOcv1 closed down 3.4 percent at 444 yuan ($67) a tonne, after falling as low as 437 yuan.
"We are getting less orders especially from the northern steel mills," said a Beijing-based iron ore trader. "But our cargoes are mainstream so liquidity is still okay."
By mainstream, the trader meant her company sells high-quality Australian iron ore which is mostly preferred by mills across China as it boosts productivity at their plants and can reduce emissions as less coke is used in the production process.
Still, overall iron ore consumption in China could drop by 77.65 million tonnes if all 28 cities covered by the restrictions cut production by half, Cao Ying, analyst at SDIC Essence Futures, has estimated. represents almost 8 percent of China's 2016 imports.
Coking coal futures DJMcv1 slumped 6.4 percent to 1,097 yuan per tonne and coke DCJcv1 fell 7 percent to close at 1,687 yuan, after hitting a 3-1/2-week low of 1,683 yuan.
The most-active rebar contract on the Shanghai Futures Exchange SRBcv1 fell 3.5 percent to 3,604 yuan a tonne.
China's crude steel output rose 5.3 percent from a year earlier to 71.83 million tonnes in September, down from a record 74.59 million tonnes in August, as mills curbed production in line with Beijing's campaign for clearer skies. = 6.6213 Chinese yuan)