* Jan-Sept crude imports from Iran at 570,350 bpd, up 33 pct on yr
* Sept supplies from Russia up 57 pct on yr at 691,310 bpd
* First Libyan imports this year at 34,067 bpd (Adds Russia, Libya imports, background)
BEIJING, Oct 22 (Reuters) - China's September crude oil imports from Iran rose 5.8 percent from a year earlier to 503,261 barrels per day (bpd), in an expected rebound after a fall in the previous month, customs data showed on Wednesday.
For the January-September period, imports rose 33.2 percent over the same level a year ago to 570,350 bpd, the data showed. China is Iran's top oil buyer and has been the most aggressive in raising its crude purchases after an easing of the Western sanctions aimed at ending Tehran's disputed nuclear programme.
Iran and the United States said last week they made some progress in high-level nuclear talks aimed at reaching a final resolution to the decade-old dispute but that much work remained to clinch a deal by a late-November deadline.
China's September imports from Iran rebounded from August's 311,653 bpd, the lowest level since October 2013 as one regular buyer went into an overhaul at its petrochemical plant.
China also boosted its imports from Russia last month, with supplies recorded at 691,310 bpd, the third highest on record on a daily count and up 57 percent from a year ago.
Chinese refiners may have taken advantage of a weak market for Russia's flagship export crude ESPO, for which premiums sank to their lowest in four years in August.
With January-September shipments up 27 percent on year, Russia ranked as China's third-largest supplier after Saudi Arabia and Angola for the year so far.
China also took in around 34,067 bpd of crude oil from Libya, its first shipments from the OPEC nation this year after oil productions there recovered from nationwide strikes that had crippled the industry.
China's total crude oil imports rose 7.4 percent on year in September to the second highest level on record at 6.71 million bpd, as state oil companies stepped up their purchases in a falling crude market to build inventory stockpiles.
1 tonne=7.3 barrels Reporting by Adam Rose and Chen Aizhu; Editing by Tom Hogue