South Korea has said it will suspend all imports of Iranian oil from July 1 amid a European Union (EU) insurance ban on vessels carrying the product. The insurance ban is part of a series of measures taken by the EU and the US to hurt Iran's oil exports. Oil is a major source of revenue for Tehran, and the EU and US have been trying to use it as a tool to persuade Iran to give up its nuclear programme. South Korea is the first major Asian economy to halt oil imports from Iran.