Stocks fell at the open Monday in Tokyo after conflict escalated over the weekend in the Middle East and the price of oil jumped, while the yen also weakened as traders and investors evaluated its safe haven status in the current environment.

The Nikkei 225 stock average dropped about 2% at the open and was down about 1% an hour later. Japanese government bonds strengthened slightly, and the country’s currency was volatile at the open but overall little changed as trading continued.

The United States and Israeli armed forces attacked Iran over the weekend in a massive assault that killed Ayatollah Ali Khamenei, the nation’s supreme leader for nearly four decades.

The attacks triggered retaliatory strikes against multiple targets in the Middle East. Flights were halted in the region, and vessels have been forbidden from navigating the Strait of Hormuz — 20% of the world’s crude oil is transported through the strait.

In New York trading, crude oil futures were up about 12% from Friday, hitting an eight-month high of $75.33 per barrel. Prices settled back as trading continued Monday morning.