U.S. strikes on Iran's nuclear sites could heighten the threat to American operators in the region, an organisation that monitors flight risks warned on Sunday, as some airlines cancelled flights to and from Dubai and Doha.

The United States decisively entered into conflict with Iran on Saturday after President Donald Trump ordered US warplanes to drop massive bombs on three nuclear sites inside the country, thrusting him squarely into an escalating Middle East conflict even as he holds out hope the matter can be resolved diplomatically.