The two separate attacks in Aden - one claimed by the Houthis - killed and wounded dozens on Thursday, security sources reported.
A Reuters witness saw nine bodies on the ground after an explosion hit a military camp belonging to the Yemeni Security Belt forces backed by the United Arab Emirates, which is a member of the Saudi-led military coalition battling the Houthis.
The attack killed at least 49 people, a health ministry official said. Medecins Sans Frontieres tweeted that tens of wounded people were hospitalized.
Soldiers screamed and ran to lift the wounded and place them on trucks. Red berets lay on the ground in pools of blood.
The Houthi's official channel Al Masirah TV said the group had launched a medium-range ballistic missile and an armed drone at the parade, which it described as being staged in preparation for a military move against provinces held by the movement.
The parade “was being used to prepare for an advance on Taiz and Dalea”, Masirah cited a Houthi military spokesman as saying.
A pro-government military source and security sources said a commander, Brigadier General Muneer Al-Yafee, a leading figure of the southern separatists, was among those killed.
"The blast occurred behind the stand where the ceremony was taking place at Al Jalaa military camp in Buraiqa district in Aden," the Reuters witness said. "A group of soldiers were crying over a body believed to be of the commander."
Yafee had just stepped off the stage to greet a guest when the explosion took place. Flags of the former South Yemen and those of leading coalition members were fluttering as the military band was waiting for its cue to start playing.
In a separate attack in another district of Aden on Thursday, an explosives-laden car blew up at a police station in the city’s Omar al-Mokhtar neighborhood, killing three soldiers.
Sources say at least 20 people were wounded, including three civilians.
The bomber drove into the police station’s gates shortly before the morning police lineup before the start of the workday.
The officials spoke on condition of anonymity because they weren’t authorized to talk to reporters and the witnesses declined to identify themselves for fear of reprisals.
Saudi Arabia's envoy to Yemen accused Iran of being behind the attack on the military parade.
Mohammed bin Saeed Al-Jabir, in a Twitter post, also blamed Iran for the attack on a police station.
The Houthi attack on Aden is a strong indicator of their unified goals with Daesh and Al-Qaeda, the envoy said.
Yemen's Prime Minister Maeen Abdulmalik Saeed, in separate tweets, said the attacks were coordinated under "Iran's administration".
He addded that the Houthis continue to implement the agendas of Iran.
It was not clear if the incidents were related. Previous car attacks in Yemen have been carried out by militant groups like Al-Qaeda.
In February last year, twin suicide bombings claimed by Daesh hit a base of an Aden counter-terrorism unit, killing five people, including a child.
Five months later, two people were killed when an attacker blew himself in the city.
Aden is the seat of Yemen’s internationally recognized government, which has been at war with the Houthis since 2015.