The Iranian-backed Houthis distributed photos apparently showing the killings. Hundreds of people attended the execution, mostly Houthis and their supporters.
The nine were among 17 people convicted for the killing of Saleh al-Sammad, head of the Houthis' supreme political council. The convicts' list includes former US President Donald Trump, too.
A redeployment of the missiles had been rumoured for months, in part due to a desire to face what American officials see as the looming “great powers conflict" with China and Russia.
The rebels have accelerated their push to take Marib in recent months, while escalating cross-border attacks on Saudi Arabia, which leads the military coalition opposing them.
The Houthi rebels, who control significant parts of the civil war-ravaged Yemen, have imposed an information blackout on confirmed cases and deaths from COVID-19.
Saudi Arabia said a ballistic missile intercepted over Riyadh Tuesday was "Iranian-Huthi", days after Washington accused Tehran of manufacturing a missile fired by the Yemeni rebels.
Saudi Arabia intercepted a Yemeni rebel missile over Riyadh today, state media said, as the rebels said the target was Yamamah palace, the official residence of King Salman.