SANAA, Yemen -- Saudi-led airstrikes hit a convoy of civilians fleeing the fighting in southern Yemen early Wednesday, killing at least 31 people, medical officials said, making it among the deadliest single attacks since the air campaign against Shiite rebels and their allies began nearly three months ago.

The two airstrikes hit a convoy of vehicles loaded with civilians, including women and children, who were fleeing north from the southern city of Aden, which has seen intense clashes in recent months. The medics described a scene of carnage, with body parts scattered across the highway and smoke billowing from charred vehicles.

Yemen's conflict pits the Shiite rebels known as Houthis - who seized the capital last year - and military units loyal to former President Ali Abdullah Saleh against an array of forces, including southern separatists, local and tribal militias, Islamic militants and loyalists of exiled President Abed Rabbo Mansour Hadi. The Saudi-led coalition backing Hadi began carrying out airstrikes on March 26.

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U.N.-brokered talks between the rival factions are underway in Geneva, aimed at ending the violence and addressing the humanitarian crisis in the Arab world's poorest nation. Mediators hope to achieve a humanitarian truce during the holy month of Ramadan starting Thursday, but neither side has shown any desire to compromise.

Despite nearly three months of airstrikes, the anti-Houthi forces have made little progress aside from capturing the city of Dhale, near Aden. The violence has killed at least 1,412 civilians and wounded 3,423, according to U.N. figures.

CBS News' Clarissa Ward was one one of the first western journalists to report from Yemen since the Saudi-led military campaign began. She found parts of the capital city, Sanaa, destroyed by the Saudi-led strikes, including buildings in the ancient Old City. Ward said millions are facing a humanitarian crisis as aid agencies struggle to move resources around the country due to the heavy fighting and airstrikes.

There was heavy fighting Wednesday in the oil and gas-rich Marib province east of Sanaa, where Sunni tribes have fended off a number of Houthi advances on the city of al-Saheel, security officials said.

Airstrikes targeted the Houthis in Marib as well as in Sanaa, Aden, the rebels' northern heartland and the western city of Taiz, they said.

In Taiz, Houthi shelling has killed more than 30 civilians in the past 48 hours, medical officials and witnesses said. The rebels control a third of the city.