* Dollar/yen jumps above 85 yen then retreats
* Traders cite intervention talk, which is not confirmed
* Euro rises on Ifo, resilient to sovereign debt problems
(updates prices)
By Jessica Mortimer
LONDON, Sept 24 (Reuters) - The dollar fell to its lowest in more than a week against the yen on Friday, reversing earlier gains, as doubts crept in about whether Japanese authorities keen to stem yen gains were responsible for an earlier spike.
The euro gained broadly, buoyed by stronger-than-forecast German data, while the U.S. currency stayed under selling pressure due to concerns the U.S. Federal Reserve may opt for more monetary easing to boost a flagging economy.
Coupled with reported Asian selling of dollar/yen, negative sentiment towards the greenback helped push it as low as 84.22 yen according to Reuters data.
This was its lowest level since Sept. 15, when Japanese authorities confirmed they had intervened to sell yen in the currency market.
Earlier, the dollar climbed suddenly to 85.40 yen from about 84.55 in Asian trade, sparking talk the Japanese may have intervened again.
"There was an overnight spike in dollar/yen, which sparked talk of intervention, but that has not been backed up and we have seen it dribbling back lower," said Jeremy Stretch, head of currency strategy at CIBC.
By 1121 GMT, the euro was up 0.7 percent against the dollar at $1.3408, lifted by an unexpected rise in the German Ifo business climate index, which helped offset Thursday's below-forecast purchasing mangers' survey.
"The Ifo data reversed some of the euro negativity after the weak PMI data," Stretch said.
The euro proved resilient to euro zone debt worries and record high Irish and Portuguese bond yield spreads over their German counterparts.
Traders said news Qatar and Greece signing a framework deal for the emirate to invest $5 billion in Greece helped ease some concerns about peripheral euro zone countries.
Against the yen, the dollar was around 0.1 percent lower at 84.29 yen, with traders citing options barriers at 84.25 and 85.00 yen.
The dollar also hit a two-and-a-half year low of 0.9785 Swiss francs, below a reported barrier at 0.9800 francs, with the Swiss currency helped by safe haven buying as equity markets fell.
UPWARD PRESSURE ON YEN
The euro gained 0.7 percent to 113.10 yen, having earlier jumped as high as 113.75 in tandem with the spike in dollar/yen.
Japanese officials stayed silent on whether they had intervened. Top currency diplomat Rintaro Tamaki declined to comment, Jiji news agency reported, and the Bank of Japan and the government also had no comment..
Japan intervened for the first time in six years last week in repeated action that pushed the yen down from a 15-year high of 82.87 per dollar and shunted it above 85.
The dollar stayed above 85.00 yen until the Federal Reserve signalled this week that it might take more quantitative easing steps, putting widespread selling pressure on the greenback and casting doubt over how effective solo intervention can be.
"With stock markets retreating and a general pullback in risk appetite, the yen and the Swiss franc will be supported, making the BoJ's job harder," said Kenneth Broux, markets strategist at Lloyds TSB Financial Markets.
Some dealers speculated an apparent lack of complaint by U.S. President Barack Obama about last week's intervention when he met Japanese Prime Minister Naoto Kan late on Thursday was seen as tacit approval by Washington of Japan's action.
Obama, who urged Chinese premier Wen Jiabao to take more action on the yuan, did not mention currencies when he met Kan, Kyodo news agency reported.
(Additional reporting by Anirban Nag)