TOKYO: Japan's top currency diplomat, Atsushi Mimura, said on Monday he was "concerned" about foreign exchange moves after the yen fell sharply against the dollar following a Bank of Japan meeting last week.

"The recent forex moves were one-sided and sharp, and I'm concerned about them" he told reporters. "We'll take appropriate actions against excessive moves."

The dollar rose as high as 157.67 against the Japanese yen on Friday, its strongest level in four weeks, after the BOJ raised rates to a 30-year-high but did not offer clarity on future hikes.