* Coal imports from Russia up 36.3 pct yr-o-yr in 2017
* Surge came after China banned coal imports from N.Korea
* Australia remains China's largest coal supplier in 2017 (Updating to add graphic)
BEIJING, Jan 25 (Reuters) - China's coal imports from Russia and Mongolia soared in 2017, customs data showed on Thursday, as the two countries filled a supply gap caused by trade sanctions on North Korea.
Arrivals from Russia <COA-RUCN-IMP> in 2017 surged 36.3 percent from 2016 to 25.3 million tonnes, data from the General Administration of Customs showed, with December figures at 2.14 million tonnes, up 16.2 percent from a year ago and 11.5 percent from November.
Imports from Mongolia <COA-MNCN-IMP> rose to 33.58 million tonnes in 2017, up 27.6 percent from 2016, while December's imports came in at 2.83 million tonnes, down 18.6 percent from a year ago but up 2.5 percent from November.
China issued a ban on coal imports from North Korea in late February, about a week after the country tested an intermediate-range ballistic missile. For the rest of the year, China only reported North Korean coal imports in August and September.<COA-KPCN-IMP>
In 2016, China brought in more than 20 million tonnes of North Korean coal, making it Beijing's fourth-largest supplier after Australia, Indonesia and Mongolia.
"The majority of market share left by North Korea was grabbed by Russia, as mining costs in Russia are cheaper than in China's northeastern region," said Cheng Gong, an analyst at the China National Coal Association.
In 2017, Australia was China's largest coal supplier for a sixth year in a row, bolstered by increasing demand for high-grade supplies due to Beijing's crackdown on air pollution.
Coal imports from Australia <COA-AUCN-IMP> rose 13.4 percent from 2016 to 79.91 million tonnes. In December, China bought 8.07 million tonnes of Australian coal, up 19.4 percent from a year ago.
Australian coal, with lower pollutants such as sulphides and ash and a higher energy value, is considered a high-grade fuel compared to Mongolian and Indian supply.
Arrivals from Indonesia COA-IDCN-IMP> in 2017 fell 9.7 percent from 2016 to 35.28 million tonnes. December imports of 1.71 million tonnes were down 63.1 percent from the same period in 2016.
In late November, Beijing eased some restrictions on coal imports to ensure stable coal supplies during the peak winter heating season.
Data released earlier this month showed China's total December coal imports rose 3 percent from November to 22.74 million tonnes.
Vessel-tracking and port data compiled by Thomson Reuters Supply Chain and Commodity Forecasts suggest China in January will import around 20.9 million tonnes of seaborne coal, both thermal and coking, up from 17.2 million in December and 19.1 million in November.
(Reporting by Muyu Xu and Josephine Mason; Editing by Christian Schmollinger)