An air strike by the Saudi-led coalition on the old quarter of the Yemeni capital killed five people on Friday and destroyed three houses in the UNESCO-listed heritage site.
Residents said the pre-dawn strike was the first direct hit on old Sanaa since the launch of the bombing campaign against Houthi rebels in late March.
The missile hit the Qassimi neighbourhood, which boasts thousands of houses built before the 11th century, an AFP journalist reported.
It did not explode but it still destroyed three three-storey houses and killed five residents, including a woman and a child, medics and witnesses said.
The target of the raid was not immediately clear amid conflicting statements from residents about whether rebels had occupied one of the houses hit.
The old city has already suffered some damage from air strikes on nearby targets, including the defence ministry, prompting a protest from UNESCO in May.
Sanaa's old city, situated in a mountain valley, has been inhabited for more than 2,500 years and was a major centre for the propagation of Islam, boasting over 100 mosques, 14 public baths and more than 6,000 houses built before the 11th century.
It was inscribed on UNESCO's World Heritage List in 1986.
The multi-storey houses rising above stone ground floors were built of rammed earth and burnt brick. Each building is decorated with geometric patterns of fired bricks and white gypsum, inspired by traditional Islamic art.