The Bank of Japan has reportedly conducted a rate check, a move typically seen as a sign that the government and the central bank are planning direct currency intervention. It comes amid the yen's sharp decline against the dollar.

Sources say the BOJ asked currency dealers on Wednesday about how the yen was trading against the dollar.

This came after the yen plunged in the morning, dropping to the upper-144 level against the dollar at one point.

Finance Minister Suzuki Shunichi said the government was concerned by the decline and could be forced to take action.

"We will not rule out any options if this sort of sudden movement continues," he said.

His comments and reports about the rate check fueled speculation the government and BOJ were planning to intervene. This brought the yen back to the 143 level.