Asian stock markets have fallen for a third consecutive day, with South Korea's Kospi index falling 3.7% and Japan's Nikkei 225 falling 2.3%. Meanwhile, oil prices have steadied as tensions rise over the crucial Strait of Hormuz, where around a fifth of the world's oil and gas usually flows from Iran. The US Navy has pledged to protect ships in the region if necessary, and will provide risk insurance to all shipping firms.