US President Donald Trump has warned that Iran will face "much harder and higher" attacks if it hits back against what he called "very justified" US strikes on the country.

"If the failed Nation of Iran retaliates for this very justified attack, they will be hit again at a much harder and higher level, but it will not be the biggest attack of them all, that is waiting in the wings and, when it is over, there will be very little left of the Islamic Republic of Iran!" Trump said on his Truth Social network.

He added that the strikes were in response to Iran laying mines and shooting missiles at an American base in Jordan.