The pre-dawn strike Friday reduced at least four historic houses in Sanaa's old city to rubble, drawing condemnation from the UN's cultural agency. Rescue workers said at least six bodies had been pulled from the debris.

"We heard screaming in the alley…after Saudi strikes hit the area," old city resident Abdullah told Reuters. "We started digging to get the victims out and six hours later managed to pull out only five [bodies] all from the same family."

The Saudi-led coalition, which has been bombing Yemen for the past 11 weeks, denied it was behind the attack on the old quarter, suggesting instead that a rebel ammunition cache may have exploded there.

Sanaa's old city was added to the UNESCO World Heritage List in 1986. The area dates back 2,500 years and is famous for its decorated ochre and white mud-brick buildings, inspired by traditional Islamic art.

"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," UNESCO Director General Irina Bokova said in a statement. "I am shocked by the images of these magnificent many-storied tower-houses and serene gardens reduced to rubble."

UN talks in Geneva

A Saudi-led coalition of Gulf states launched airstrikes against Shiite Houthi rebels in late March in an attempt to stop the rebels' advance and restore exiled Yemeni President Abed Rabbo Mansour Hadi to power.

The Houthis, who are fighting alongside forces loyal to ousted former president Ali Abdullah Saleh, have advanced rapidly across the country, seizing Sanaa and other regions in recent months.

Yemen's warring parties are due to meet on Sunday in Geneva for UN-sponsored peace talks aimed at finding a solution to the conflict and providing humanitarian aid. UN spokesman Ahmad Fawzi said the negotiations "mark an important step as the parties embark on the road towards a settlement."

Representatives from countries in the Gulf, the UN Security Council, the European Union, as well as from Egypt, Turkey, Germany, the Netherlands and Japan are expected to take part in the talks.

According to UN figures, the Saudi coalition's military campaign has left more than 1,000 civilians dead and a million people displaced.

nm/msh (Reuters, AP, AFP)