* FTSEurofirst 300 index down 0.5 pct, Euro STOXX 50 index down 0.6 pct at close
* Bayer falls on scrutiny of Xarelto drug
* Miner Anglo American extends losses on target cuts
* Fresnillo falls on burst pipeline
* Greek shares at lowest level since 2012 (Recasts, adds detail and quote, updates prices at close)
By Kit Rees
LONDON, Dec 9 (Reuters) - European shares fell on Wednesday to their lowest level in more than a month, weighed down by a drop at pharmaceuticals group Bayer and pressure on miner Anglo American.
Bayer shares fell by 2.1 percent as European and U.S. drug safety agencies probed whether a defective blood-clotting test device affected a trial involving Bayer's anti-blood clotting drug Xarelto.
The pan-European FTSEurofirst 300 index was down 0.5 percent at its close, its lowest since late October, while the euro zone's blue-chip Euro STOXX 50 index also slipped by 0.6 percent.
Oil prices climbed back up on Wednesday as U.S. crude inventories dipped, while Japan posted rising machinery orders and copper prices also held their ground.
Miners Glencore and BHP Billiton recovered to trade up 4.6 percent and 3.7 percent respectively, while Rio Tinto advanced 3.8 percent.
Nevertheless, many investors were cautious, citing persistent concerns about a slowdown in China and uncertainty over the impact of a likely U.S. interest rate hike in December.
China is the world's biggest consumer of metals, and fears about a slowdown have knocked back commodity stocks this year.
"There is no doubt that the investment community see the likes of Glencore, BHP Billiton and Rio Tinto as a bargain over the long term, yet the continued deterioration in commodity and stock prices will mean that most investors stay away until something fundamentally changes in the sector," Joshua Mahony, market analyst at IG, wrote in a note.
Anglo American, which hit another record low earlier in the session, retreated 1.2 percent, its seventh straight day of losses after a series of broker target cuts following the company's decision to suspend dividends and restructure its business.
It was joined by silver miner Fresnillo, which fell 0.9 percent after a pipeline burst at its Saucito mine, spilling about 450 tons of tailings.
Greek shares hit their lowest level since 2012, with the battered banking sector bearing the brunt of falls in the wake of an extended short-selling ban. Greece's Athex share index was down 3.8 percent at its close.
The National Bank of Greece was the main casualty on the STOXX 600 index, slumping over 21 percent.
Among top performers on the STOXX 600 index, Ashtead climbed 8.6 percent after the industrial equipment hire group raised its profit expectations.
Auto stocks were also in focus as Volkswagen rose 6.2 percent after reporting that the number of cars affected by its carbon dioxide cheating was far fewer than feared, only 36,000 vehicles as opposed to 800,000.
Shares in Porsche also rallied 5.4 percent.
In spite of the pullback so far this week, European stock markets remain in positive territory since the start of 2015, helped by economic stimulus measures from the European Central Bank (ECB).
The FTSEurofirst is up 4.7 percent since the start of 2015, while Germany's DAX is up nearly 10 percent.
Today's European research round-up (Editing by Estelle Shirbon and David Evans/Richard Balmforth)