The mysterious explosion struck the Israeli-owned MV Helios Ray, a Bahamian-flagged roll-on, roll-off vehicle cargo ship, as it was sailing out of the Middle East on its way to Singapore on Friday.
The airstrikes targeted facilities near the Iraqi border used by Iranian-backed militia groups, the Pentagon said.
State TV reported the country had officially begun restrictions on nuclear inspections, in what is seen as a bid to pressure the west into lifting sanctions and restore the 2015 nuclear deal.
The explosion at the Islam Qala crossing in Afghanistan's western Herat province caused a massive fire that consumed more than 500 trucks carrying natural gas and fuel.
The latest maritime seizure by Iran came ahead of negotiations over Iranian assets frozen in South Korean banks and amid increased tensions with the West over its nuclear program.
Iran executed a once-exiled journalist over his online work that helped inspire nationwide economic protests in 2017.