DUBAI - Saudi Arabia's Crown Prince Mohammed bin Salman said on Tuesday that Iran's supply of rockets to militias in Yemen is an act of "direct military aggression," Saudi state news agency SPA reported.The supply of rockets to the Iran-allied rebel Houthi movement could "constitute an act of war against the Kingdom," SPA quoted the crown prince as saying in a telephone call with the British Foreign Minister Boris Johnson.Saudi air defense forces intercepted a ballistic missile they said was fired towards Riyadh on Saturday by the Houthi militia which controls large parts of neighboring Yemen, including the capital Sanaa, in the country's civil war.Iran has denied it was behind the missile launch, rejecting the Saudi and US statements condemning Tehran as "destructive and provocative" and "slanders."In an interview with CNN television on Monday, Saudi Foreign Minister Adel al-Jubeir accused the armed Lebanese Hezbollah group of firing the missile at Riyadh from Houthi-held territory."With regards to the missile... that was launched on Saudi territory, it was an Iranian missile launched by Hezbollah from territory occupied by the Houthis in Yemen."He said the missile was similar to one launched in July at Yanbu in Saudi Arabia and was manufactured in Iran, disassembled and smuggled into Yemen, then reassembled by the operatives of the Iranian Revolutionary Guards and Hezbollah, "then it was launched into Saudi Arabia."In reaction to the missile, the Saudi-led military coalition fighting against the Houthi movement in Yemen said on Monday it would close all air, land and sea ports to the Arabian Peninsula country.The move is likely to deepen a humanitarian crisis in Yemen that according to the United Nations has pushed some seven million people to the brink of famine and left nearly 900,000 infected with cholera.