Iran may close the vital maritime route, through which one-fifth of the world’s oil supply is shipped every day.
Washington's support for Kyiv, already in doubt under President Trump, is set to decline further, analysts say.
Arrest comes shortly after Cyprus detains ethnic-Azeri suspected of planning attack on military base for Iran.
Belarusian opposition activist Siarhei Tsikhanouski was released after five years behind bars.
Tehran has criticised Rafael Grossi for rhetoric it believes helped pave way for strikes, mulling exit from NPT.
Move follows campaign accusing Maersk of links to Israel's military and occupation of Palestinian lands.
Donald Trump has said the images showing the aftermath of Iran’s nuclear sites following the US attack reveal "success".
Video shows protests across the world in response to US air strikes on Iran.
A senior Iranian diplomat condemned the US strikes on its nuclear sites, after attending an emergency IAEA meeting.
Many airlines have suspended flights to some Middle Eastern destinations, but others are adapting and using new routes.