The yen posted its biggest weekly gain since the 2008 financial crisis, also spurred by a weak reading of U.S. economic growth in the first quarter on Thursday and the Federal Reserve`s cautious tone this week.
The yen has gained 3 percent since Thursday when the BOJ decided to hold monetary policy steady in the face of soft global demand and the yen`s recent sharp rise. The BOJ move defied expectations for increased stimulus measures to fight deflation.
The dollar was last down 1.57 percent against the yen JPY= at 106.38 yen after hitting an 18-month low of 106.29. The dollar was off about 4.8 percent against the yen for the week, and set to post its biggest weekly loss since October 2008.
The dollar also tumbled against the euro, with the euro hitting its highest against the dollar in two and a half weeks, at $1.1459. The euro EUR= was last up 0.85 percent against the dollar at $1.1447.
"A large part of this move is the BOJ, which caught a lot of investors by surprise," said Omer Esiner, chief market analyst at Commonwealth Foreign Exchange Inc in Washington.
The dollar could fall to 105 yen in coming weeks as traders unwind "short" bets against the yen, analysts said.
European equities posted their biggest weekly drop in more than two months, with the FTSEurofirst 300 index .FTEU3 of leading European shares falling 2.2 percent and the euro zone blue chip Euro STOXX 50 .STOXX50E tumbling 3.1 percent.
MSCI`s all-country world stock index .MIWD00000PUS fell 0.4 percent.
On Wall Street, the Dow Jones industrial average .DJI closed down 57.12 points, or 0.32 percent, to 17,773.64. The S&P 500 .SPX slid 10.51 points, or 0.51 percent, to 2,065.3 and the Nasdaq Composite .IXIC fell 29.93 points, or 0.62 percent, to 4,775.36.
Rahul Shah, chief executive of Ideal Asset Management in New York, said valuations are high, so earnings must exceed that bar for the market to go higher.
"We`ve seen that from Amazon and Facebook, and those shares have been awarded accordingly," Shah said. "But the rest of the earnings reports have been less inspiring to say the least, so it`s hard to see the overall market march much higher."
Amazon (AMZN.O) shares jumped 9.6 percent to $659.59 a day after the company reported profit and revenue that blew away analysts` estimates, along with doubts about the online retailer`s investment spree.
Facebook (FB.O) earlier in the week reported revenue rose more than 50 percent, driving its shares up more than 7 percent on Thursday. Facebook rose 0.7 percent to $117.58 on Friday.
Brent crude trimmed gains after its biggest monthly rise in seven years. It touched 2016 highs as a weak dollar and falling U.S. production tempered concerns about an oil glut.
A looming rise in Middle East output capped gains, but investor sentiment held the optimism that has helped lift oil futures nearly 80 percent from January lows.
Brent futures LCOc1 settled down 1 cent at $48.13 a barrel, down 0.62 percent and U.S. crude CLc1 settled down 11 cents at $45.92.
U.S. gold futures GCv1 for June delivery settled up 1.9 percent at $1,290.50 an ounce, while spot prices reached a 15-month high of $1,296.76.
U.S. Treasury prices pared losses to rise, with the benchmark 10-year note US10YT=RR trading up 3/32 in price to yield 1.8280 percent.
Germany`s benchmark Bund DE10YT=TWEB yield rose sharply towards six-week highs, as the yield gained as much as 5 basis point to 0.305 percent.
More about:
