* Dollar/yen back above 117 after sliding to 115.97 overnight
* Report of official saying Tokyo watching market closely buoy USD
* Euro steady, outcome of ECB policy decision awaited
By Shinichi Saoshiro
TOKYO, Jan 21 (Reuters) - The dollar came off a one-year low against the yen on Thursday after a media report suggested Japanese authorities are becoming increasingly anxious about the strength of the local currency.
The dollar was up 0.2 percent at 117.16 yen JPY= after descending to 115.97 overnight, its lowest level since January 2015.
The U.S. currency had plummeted as a plunge in oil prices to near 13-year lows and an ensuing rout in global equities intensified demand for the safe-haven yen.
But an overnight report by Bloomberg quoting an unnamed Tokyo official that authorities were "closely watching the currency markets" lifted the dollar off one-year lows, traders said.
One of the pillars of the "Abenomics" policies under Japanese Prime Minister Shinzo Abe was to weaken the yen in an attempt to help the economy, and authorities are generally seen to be wary towards the currency appreciating excessively.
"That a Japanese official was reportedly prompted to speak on the yen was likely due to the excessive move seen on Wednesday, rather than the fact that dollar/yen fell into the 115 threshold," said Masafumi Yamamoto, chief FX strategist at Mizuho Securities in Tokyo.
The euro was flat at $1.0878 EUR= after pulling back from an overnight high of $1.0976 following the dollar's surge against the yen.
Focus was on the European Central Bank's policy decision due later in the day. The central bank is expected to keep all interest rates on hold but highlight increasing growth and inflation risks, raising the prospect of further policy easing later this year. dollar index .DXY was up 0.1 percent at 99.177 after probing a low of 98.626 on Wednesday.
The Australian dollar, battered earlier in the week amid the tumult in global risk assets and commodities, was up 0.5 percent at $0.6944 AUD=D4 following a mild rebound in crude oil prices. (Editing by Sam Holmes)