The yen soared to a 40-month high against the dollar Tuesday, prompting the Bank of Japan to step in to block it from advancing further.

With the overnight upswing in the yen's value in overseas markets carrying over into Tokyo interbank trading, the dollar fell to 106 yen in early morning trading, its lowest level since May 15, 1996.

The BOJ intervention drove the dollar back to 107.04-06 yen at noon, but the greenback soon slid back to settle at 106.55-58 yen at 5 p.m., compared with 107.77-80 yen late Monday.