Tokyo stocks have plummeted, with the nikkei 225 index falling over 700 points and another measure breaching 68,000, amid rising tensions in the middle east. The situation is reportedly driven by iran's actions, including a declared closure of the strait of hormuz, which has led to a surge in crude oil prices. The market volatility has also affected currency exchange rates, with the dollar/yen holding firm and the yen falling to a low range.