A suicide bomber blew up a vehicle outside a presidential palace in southeastern Yemen Saturday, killing 20 elite Republican Guards, under the command of outgoing president Ali Abdullah Saleh's son Ahmed, medics and a military official said.

"The bodies of 20 soldiers were taken to the mortuary and there are many others wounded," said a medic at the Ibn Sina hospital in the Hadramawt provincial capital Mukalla.

A military official said that "a pick-up truck driven by a suicide bomber exploded at the entrance of the presidential palace in Mukalla" as Abdrabuh Mansur Hadi was sworn in as the first new president in Sanaa since 1978.

A health official said the fatalities in the city of al-Mukalla were presidential guards. A security official said it was a suicide blast. He did not provide a death toll.

Both officials spoke on condition of anonymity as they were not allowed to speak to the press.

Southern separatists and Islamist insurgents are active in the region.

Hadi, who was Saleh's vice president, was formally inaugurated following a single-candidate presidential election earlier in the week.

In his televised speech, Hadi swore to keep up Yemen's fight against al-Qaida-linked militants, who took advantage of the country's upheaval to seize control of several parts of the country.

He also pledged to work to bring home the thousands of internal refugees created by fighting between government troops, southern separatists, mutinous military units, tribal movements, and numerous other factions.

"One of the most prominent tasks is the continuation of war against al-Qaida as a religious and national duty, and to bring back displaced people to their villages and towns," Hadi said.

"If we don't restore security, the only outcome will be chaos."

Source: The Associated Press and Agence France-Presse