A Saudi-led air raid on Friday killed five people and destroyed several houses at the United Nations Organization for Education, Science and Culture (UNESCO) World Heritage site in the Old City of Sana'a in Yemen, according to the BBC.

"The pre-dawn air strike destroyed five houses completely and damaged many others in the city UNESCO calls a 'jewel' of Islamic culture," reported Saba .

The Saudi-led coalition airstrike was the first direct attack on Sana'a since the American-backed group began air raids against rebel Houthi militias in Yemen in late March, according to Saba.

UNESCO condemned the destruction of several houses, saying that the world heritage site belongs to all humans.

"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," said UNESCO Director General Irina Bokova in a statement. "I am shocked by the images of these magnificent, many-storeyed tower-houses and serene gardens reduced to rubble. This destruction will only exacerbate the humanitarian situation, and I reiterate my call to all parties to respect and protect cultural heritage in Yemen."

Meanwhile, the anti-rebel coalition denied claims that its airstrike targeted the Old City of Yemen capital.

"For sure we did not conduct any operation inside [the] city," said coalition spokesman Brigadier General Ahmed, according to the AFP. "Several days before, [the Houthis] had an explosion in one of their storage areas. So it could be one of these."

In a related development, the United Nations postponed Yemen peace talks to Monday, and announced that the U.N. special envoy would hold separate talks with two rival groups in Geneva on Sunday to bring them to the same table, according to Arab News.