* Traders cite Intervention talk but no confirmation

* Euro rises on IFO, resilient to sovereign debt problems

(updates prices)

By Anirban Nag

LONDON, Sept 24 (Reuters) - The dollar spiked above 85.00 yen on Friday on talk of intervention by Japanese authorities keen to stem the yen's recent gains, but quickly retreated as doubts emerged about whether they had taken action.

That left investors nervous about more intervention and, with risk aversion hitting markets, traders said the Bank of Japan's task of weakening the yen was becoming even tougher.

The dollar rose as high as 85.40 yen JPY= from about 84.55 before talk of intervention emerged, climbing more than one yen from 84.34 yen. It later retreated to 84.26 yen, a one-week low and down 0.1 percent for the day.

"The price action certainly suggested that the Japanese Intervened, but one can't be sure," said Kenneth Broux, markets strategist at Lloyds TSB Financial Markets.

"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."

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. [ID:nTKU106266].

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.

"At these levels, one can expect the Japanese to intervene," said Lee Hardman, currency economist at BTM-UFJ. "Certainly the stronger fundamentals support a stronger yen, but I guess the Japanese Authorities will be keen to draw a line in the sand .