ABOARD AIR FORCE ONE, July 09 (BSS/AFP) - President Donald Trump warned Wednesday that US bombing of Iran will increase significantly if Tehran continues to attack ships in the Strait of Hormuz.

"This is in retribution for yesterday's bombing of ships by Iran. If it happens again, it will get much worse!" the US president posted on social media over a picture of an apparent bombing of a site in Iran.

Trump reinforced that message when speaking with reporters aboard Air Force One, returning from a NATO summit in Turkey.

"We just hit them very hard, and I say we hit them 20 to one. Every time they hit us, we're going to hit them 20," Trump told reporters. "And we did it last night. They did a little something today, but it was really retribution for last night."