SANAA: Yemeni army units allied to the Houthi militia on Thursday fired a ballistic missile toward a Saudi air base, the group's television channel said, escalating six months of war between the kingdom and the Iran-allied group.

"The missile unit of the Yemeni army fired a Scud missile toward Khaled bin Abdulaziz base at Khamees Mushait," Houthi-run Al Maseera TV reported on its Twitter page.

Residents in the capital, Sanaa, reported hearing a big roar rousing them from their sleep at around 6 a.m. as the Scud was launched near the city.

It was unclear if the weapon hit its target or caused any casualties.

Saudi Arabia led an Arab military intervention against the Houthis and their allies in Yemen's army beginning on March 26 to restore the Yemeni government ousted by the group and fend off what it sees as the creeping influence of Iran, the Shi'ite Muslim group's main ally.

The Houthis say their rise to power is a revolution against corrupt officials beholden to Saudi Arabia and the West.

Air strikes and ground fighting have killed at least 5,400 Yemenis, according to the United Nations, but near daily air attacks by the Arab alliance on Yemeni missile depots appear not to have exhausted their supply.

A powerful Cold War-era weapon, the Scud had been launched at Saudi Arabia by Yemeni forces at least three times before, but was shot down by American-provided Patriot missiles.