Saudi and Houthi media said drones belonging to the rebels hit a parade in Lahaj province, killing at least six soldiers. Eyewitnesses say high-ranked officials including Yemen's deputy chief of staff were wounded in the attack.
A bomb-laden drone flown by Yemen's Houthi rebels flew into a military parade on Thursday in Lahij outside of the southern port city of Aden.
The brazen attack killed at least six troops from a Saudi-led coalition and their allies, threatening UN-brokered peace efforts to end the yearslong war tearing at the Arab world's poorest nation.
"Once again this proves that the Houthi criminal militias are not ready for peace and that they are exploiting truces in order for deployment and reinforcements," Yemen's Information Minister Moammar al Eryani, who said two senior military officials were wounded in the attack.
The attack at the Al-Anad Air Base, where American special forces once led their fight against Yemen's al Qaida branch, targeted high-ranking military officials in Yemen's internationally-recognised government. Some 8,000 soldiers had been taking part in the parade, as well as two governors and a large number of top military commanders including the chief of staff.
Military Intelligence Chief Mohamed Tamah and commander of the fourth military zone Fadl Hassan were among the wounded in the attack at the Anad Air Base, said the source, who spoke on condition of anonymity due to restrictions on talking to the media.
"This is time for the international community to stand by the legitimate government and force the militias to give up their weapons and pull out of the cities," Eryani added.
The Houthis immediately claimed the attack through their al Masirah satellite news channel, saying the attack targeted "invaders and mercenaries", leaving "dozens of dead and wounded."
The rebels, who claimed to possess five different drone models, said in November they were halting drone and missile attacks on Saudi Arabia, the United Arab Emirates, and their Yemeni allies.
Iran has been accused by the US and the UN of supplying ballistic missile technology and arms to the Houthis, something Tehran denies.
Last month, Houthi rebels and government officials agreed to a UN-brokered ceasefire in the flashpoint Red Sea port city of Hudaida, a key gateway for aid and food imports to Yemen.
The ceasefire went into effect on December 18, but has remained shaky with the two sides accusing each other of violations.
The UN humanitarian aid chief Wednesday accused the rebels of blocking humanitarian supplies travelling from areas under their control to government-held areas. Mark Lowcock told the UN Security Council that the rebels also recently informed humanitarian agencies that 72 hours' notice is required ahead of any movements instead of 48 hours.
Tens of thousands have been killed since Saudi Arabia and its allies joined the government's fight against the Houthis in 2015.
More than 22 million people – three-quarters of the population – now depend on humanitarian assistance to survive.