At least 30 Yemeni soldiers were killed in coalition air raids and clashes after troops attempted to defect to Iran-backed rebel ranks near the border with Saudi Arabia, a military source said Wednesday.

Saudi-led coalition jets, which have bombed Yemeni rebel positions since March, intervened when "dozens of soldiers defected and announced their support" for Shia Houthi rebels on Tuesday, prompting clashes with pro-government troops, the source said.

The incident took place at the 23rd Mechanised Brigade, stationed near the border with Saudi Arabia and left "at least 30 soldiers killed and dozens wounded" on both sides, he told AFP.

"Armoured vehicles and troop carriers were destroyed or damaged" in the air raids and clashes between rival units before the situation was brought under control, the source added.

Troops loyal to former president Ali Abdullah Saleh have joined forces with the Houthi rebels, who seized the capital almost unresisted in September before advancing southwards in the impoverished Gulf country.

Saudi Arabia fears the Houthis are trying to bring Yemen under the influence of Shia Iran.

In the country's main southern city of Aden, heavy fighting raged between rebels and pro-government forces, residents said.

Military sources said that the rebels fired rockets at a residential district killing eight civilians, among them three children.

AFP could not confirm the toll from medical sources.

Meanwhile, the rebel-controlled sabanews.net website reported that around 40 inmates escaped in a jailbreak after coalition jets bombed the area surrounding a prison in Mahawit province, northwest of the capital.

The UN says more than 3,200 people have been killed and 1.26 million displaced in Yemen since fighting broke out in March.