* Oct aluminum output falls 7.5 pct on-year
* Jan-Oct aluminum output still up 3.7 pct on-year
* Oct nonferrous output down 3.3 pct at 4.46 mln T
* Year-to-date nonferrous output up 3.4 pct
BEIJING, Nov 14 (Reuters) - China's primary aluminum production fell for a fourth straight month in October, government data showed on Tuesday, hit by high costs and the closure of illegal capacity, with further decreases expected soon as winter output restrictions kick in.
The world's top aluminum producing country churned out 2.55 million tonnes of the metal last month, down 2.3 percent from 2.61 million tonnes in September and versus 2.73 million tonnes in October, 2016, according to the National Bureau of Statistics (NBS).
Year-to-date aluminum production came in at 27.23 million tonnes, up 3.7 percent year-on-year.
China's aluminum production has been declining since June's record-high of 2.93 million tonnes following the closure of illegal smelting capacity.
It remains on course for a record-high in 2017, but the year-on-year growth rate has slowed dramatically from double digits in February-April.
Output is set to dip further in the coming months as China imposes its first ever winter restrictions on aluminum production, part of the government's battle against pollution.
However, the cuts, which are getting under way in smog-prone cities as northern China's heating season begins this week, may not be as severe as initially expected.
China's overall non-ferrous metals output in October came in at 4.46 million tonnes, up from 4.44 million tonnes in September and versus 4.55 million tonnes in October, 2016.
Year-to-date nonferrous production stood at 45.22 million tonnes, up 3.4 percent from the same period last year and still on course for a record-high. (Reporting by Tom Daly in Beijing and Ruby Lian in Shanghai; Editing by Joseph Radford)