A suicide car bombing has killed 26 people outside a presidential palace in southern Yemen hours after longtime vice president Abd-Rabbu Mansour Hadi was sworn-in as the country's new leader.

Security officials say at least 26 people were killed and at least 20 wounded in Saturday's bombing, which occurred in southern Hadramawt province, located about 400 kilometers southeast of the capital, Sana'a.

The bombing took place as Mr. Hadi faces the challenge of uniting a country heavily marked by divisiveness. Yemen has long dealt with a separatist insurgency in the south, Shi'ite rebels in the north and an active wing of al-Qaida.

Mr. Hadi, who took his oath in front of parliament Saturday, pledged to continue the fight against the Islamist militant group and bring those displaced by Yemen's crisis back to their homes.

Mr. Hadi received more than 99 percent of the votes cast in this week's single-candidate presidential election. He will preside over a two-year transition period that envisions parliamentary elections, a new constitution and restructuring of the military. The handover cements a U.S. and Gulf-backed power transfer deal under which former president Ali Abdullah Saleh agreed to step down in return for immunity.

Mr. Saleh arrived back in Sana'a early Saturday after receiving medical treatment in the United States for injuries suffered during an assassination attempt. He is expected to formally hand over power during a ceremony at the presidential palace in Sana'a on Monday.