ADEN - At least 20 people were killed and dozens wounded in an attack on Aden airport on Wednesday moments after a plane landed carrying a newly formed cabinet for government-held parts of Yemen.

Hours after the attack, a second explosion was heard around Aden's Maasheq presidential palace where the cabinet members including Prime Minister Maeen Abdulmalik, as well as the Saudi ambassador to Yemen, had been taken to safely, residents and local media said.

In the airport attack, loud blasts and gunfire were heard shortly after the plane arrived from Riyadh, witnesses said. A local security source said three mortar shells had landed on the airport's hall.

Aden health official Mohamed Robeid gave the death figure and said 50 people were wounded, adding the death toll could rise. Medecins Sans Frontieres aid group earlier said 17 people had been treated for wounds at its hospital in Aden.

There was no claim of responsibility.

It was unclear what caused the second blast and there were no immediate reports of casualties.

"We and the members of the government are in the temporary capital of Aden and everyone is fine," Maeen tweeted from Maasheq palace. "The cowardly terrorist act that targeted Aden airport is part of the war that is being waged against the Yemeni state and its great people."

Jaber tweeted: "Peace, security and stability will prevail thanks to Yemenis' strong will and their brave government."

The new cabinet unites the government of President Abd-Rabbu Mansour Hadi with southern separatists, intended to fulfil a Saudi aim of ending a feud among Riyadh's allies.

The two groups are the main Yemeni factions in a southern-based, Saudi-backed alliance fighting the Iran-aligned Houthi movement that controls the north, including the capital Sanaa.

TV footage from Saudi-owned Al Arabiya channel showed dozens of people leaving the airplane when a first blast hit the airport's hall. Heavy gunfire from armoured vehicles followed with plumes of white and black smoke rising from the scene.

Other video showed damage to the terminal's concrete walls and smashed glass.

Government officials were among the casualties in the airport attack, sources said.

The southern port city of Aden has been mired in violence because of a rift between the separatists and Hadi's government, based there after being driven from the capital by the Houthis in 2014.

The separatist Southern Transitional Council (STC), which seeks independence for south Yemen, declared self-rule in Aden in April, triggering clashes and complicating United Nations efforts to forge a permanent ceasefire in the overall conflict.

The Saudi-led coalition announced the new power-sharing cabinet this month after more than a year of intense Saudi mediation between the government and the separatists.

The Houthis denied any responsibility for the attack. The separatists said their leadership was the main target of the attackers and not the government.

UN Yemen envoy Martin Griffiths condemned the attack in a statement.

"I wish the cabinet strength in facing the difficult tasks ahead," he said. "This unacceptable act of violence is a tragic reminder of the importance of bringing Yemen urgently back on the path towards peace."

Reuters