* Yen falls back from 15-year high on intervention wary
* World stocks fall for 5th day straight
By Dominic Lau
LONDON, Aug 25 (Reuters) - The yen eased from a 15-year high on Wednesday on a report that Tokyo was considering weakening its currency, while world stocks fell for the fifth day on concerns over the global economy sliding back into recession.
However, a better-than-expected German business sentiment reading from think tank Ifo helped lift European shares into the black.
Crude prices also bounced from a seven-week low as investors looked for relief in U.S. durable goods and oil inventory reports due later in the day, though safe-haven gold prices steadied.
Nikkei business daily reported Japan's Ministry of Finance may consider unilateral yen-selling market intervention if speculators drive up the currency. The dollar has lost nearly 9 percent against the Japanese currency this year. [ID:nN24264334]
Finance Minister Yoshihiko Noda reinforced that view, telling reporters that recent yen moves were one-sided and Tokyo will respond appropriately when necessary. [ID:nTKU106216]
But some in the market said it was unlikely the Japanese would intervene at current levels.
"I think it's unlikely there would be intervention much above 80 yen," said Ray Farris, chief currency strategist at Credit Suisse in London.
"Price action is not disorderly and the yen is not overvalued by our estimates."
The dollar was up 0.7 percent at 84.56 yen JPY=, though it was down 0.2 percent against a basket of currencies .DXY.
The yen also fell from a nine-year peak against the euro.
However, Tokyo's Nikkei average .N225 lost 1.7 percent to hit a 16-month closing low on disappointment over the lack of policy action by the authorities to rein in the strong yen, which threatens a fragile economic recovery.
Illustrating the concerns over global growth, miner BHP Billiton (BLT.L) (BHP.AX) said it was cautious on the short-term outlook and that the economy in China, its biggest customer, would slow from recent highs. [ID:nSGE67O017]
World equities measured by the MSCI All-Country World Index .MIWD000000PUS dropped 0.2 percent for the fifth straight session, and the Thomson Reuters global stock index .TRXFLDPIPU lost 0.2 percent.
Europe's FTSEurofirst 300 .FTEU3 drifted 0.1 percent higher, aided by the Ifo results. [ID:nBEB004473]
A one-notch downgrade of Ireland's debt rating by Standard & Poor's sent a reminder of the problems that the euro zone peripheral economies faced with their debt. The cost of protecting Irish government bond from default rose, with the five-year credit default swaps up 3 basis points (bps) to 310 bps.
The 10-year Irish/German government bond yield spread IE10YT=TWEB DE10YT=TWEB widened by 4 bps to 334 bps.
"The strong corporate earnings we got during the summer had eclipsed the euro zone's sovereign debt fears in investors' minds, but this downgrade is a reminder that the problems have not gone away," said Christian Jimenez, fund manager and president of Diamant Bleu Gestion in Paris.
Yields on benchmark 10-year German Bunds were up 2 bps at 2.206 percent, while those on 10-year U.S. Treasuries US10YT=RR were up 2 bps at 2.5163 percent.
Oil prices CLc1 rebounded 0.9 percent to trade above $72 a barrel and copper MCU3 also recovered from a 1.6 percent drop on Tuesday following a record fall in U.S. existing home sales. (Additional reporting by Kevin Plumberg in Hong Kong, Neal Armstrong and Ian Chua in London, and Blaise Robinson in Paris; editing by Stephen Nisbet)