What missile was shot down over Riyad on March 28 in 2020 ?
 

"The Royal Saudi Air Defense Forces intercepted and destroyed a ballistic missile launched by the Houthi militia in Yemen on March 28 toward targets in the city of Riyadh, the Arab Coalition confirms in a statement. The Houthis in Yemen took credit for the attack. They said Zulfiqar missiles were used". (only ?)
Finding the engine of the projectile intercepted over Riyadh makes it possible to determine the type of this missile. A published photo clearly identifies a type of an Isayev S2.720 engine uses for the second stage of an SAM S-75M "Volkhov"
A modified missile of this type is in possession of the Houthis. It is known as the  Qaher M2  . This SAM is accelerated by a solid-fuel booster. The second stage with the S2.720 engine uses the liquid fuel combination TG-02 / AK-20K.
The SAM is a short-range anti-aircraft missile. The more mysterious is the fact that Riyadh could be reached.

Qaher M2