SANA'A, Yemen - As a Saudi-led air coalition continued to strike rebel targets across Yemen, reports emerged Saturday of more civilian casualties and of al-Qaeda-linked militants executing dozens of soldiers as they consolidated their grip on a southeastern provincial capital.

Sunni Muslim Saudi Arabia is spearheading efforts to crush the Shiite Muslim insurgents known as Houthis and restore to power the country's internationally recognized president, Abdu Rabbu Mansour Hadi. Fighting has raged for days in and near the southern port of Aden, Yemen's second city and its main commercial hub.

Hadi took shelter in Aden after the capital, Sana'a, fell to the Houthis last year, and the rebels' offensive against the port city triggered the Saudi-led intervention.

International agencies have expressed growing alarm over rising civilian casualties. The U.N. said last week that two weeks of fighting has killed more than 500 people, many of them civilians and nearly 100 of them children.

On the outskirts of Sana'a, nine people from one family were reported killed when their home was hit, apparently by an errant strike. Officials said Saturday that the strike a day earlier in Bani Matar also wounded five other family members, and that the dead and injured included five children under age 5.

The fighting appeared to be fiercest in Aden, where airstrikes have been concentrated, ground clashes are taking place between Hadi loyalists and Houthis, and warships from countries including Egypt have shelled Houthi positions. Warplanes have dropped supplies to the city's defenders, a Saudi military spokesman said in Riyadh on Friday.

The most recent round of airstrikes hit positions held by troops loyal to deposed strongman Ali Abdullah Saleh, who has allied himself with the insurgents. Aid groups have warned of a looming humanitarian catastrophe in the city, where corpses of those killed in urban fighting - some Houthis, some members of the so-called popular committees fighting them - have been left in the street.

Yemen's al-Qaeda affiliate has capitalized on the turmoil to seize new territory for itself. Last week, its fighters surged into the southeastern town of Mukalla, the country's fifth-largest city, staged a jailbreak, and looted the local branch of the Central Bank.

On Saturday, officials reported that the al-Qaeda-linked militants had executed dozens of captured soldiers in the Arabian Sea port, seizing weapons and oil shipments and overrunning military bases.