UNESCO condemned an air strike by the Saudi-led coalition on Old Sanaa Friday, a heritage site in Yemen's capital it described as "one of the world's oldest jewels" of Islamic culture.
"This destruction will only exacerbate the humanitarian situation and I reiterate my call to all parties to respect and protect cultural heritage in Yemen," said UNESCO director general Irina Bokova in a statement.
"I am profoundly distressed by the loss of human lives as well as by the damage inflicted on one of the world's oldest jewels of Islamic urban landscape."
The pre-dawn air strike by the Saudi-led coalition killed five people and destroyed three houses in the UNESCO-listed site.
Residents said it was the first direct hit on old Sanaa since the start 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.
"I am shocked by the images of these magnificent many-storeyed tower-houses and serene gardens reduced to rubble," said Bokova.
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 included 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.
"The historic value and memories enshrined in these sites have been irreparably damaged or destroyed," said Bokova.