The leaders of industrialized nations were racing on Wednesday to shore up the global oil supply, after three ships in the Persian Gulf and Strait of Hormuz came under attack, in a stark illustration of how the war in the Middle East is threatening to choke off one of the key conduits for international trade. Japan, Germany and Austria will release oil from their strategic reserves in response to disruptions in the supply from the Middle East, officials in those countries said on Wednesday. They made the announcements hours before a meeting of leaders of the Group of 7 industrialized nations, including the United States, to discuss jointly releasing oil in consultation with the International Energy Agency. The attacks, which occurred within a few hours of each other, marked a sharp uptick in strikes on vessels in or near the Strait of Hormuz, through which a fifth of the world’s oil transits. On Tuesday, the U.S. military said that it had attacked 16 Iranian mine-laying vessels near the strait, where tanker traffic has been largely paused for days because of concerns that drones or missiles could hit merchant ships.