Houthi fighters in Yemen say they are establishing their own government of "national salvation" to rival the internationally recognised administration of President Abd Rabbu Mansour Hadi in the south.
The move was decided by a "supreme political council" created in July by the Iran-backed group and forces allied to Yemen's former president Ali Abdullah Saleh.
On Sunday, Saleh al-Sammad, head of the supreme political council, appointed Abdel Aziz Saleh Habtour "prime minister", the Houthis announced on their website sabanews.net.
Habtour is a former governor of the southern port city of Aden and a member of the political bureau of Saleh's General People's Congress.
READ MORE: Houthis claim attack on UAE military vessel
The announcement of a rival government is likely to further complicate the prospects of a political settlement in Yemen.
It coincided with the presence in the Saudi capital, Riyadh, of Ismail Ould Cheikh Ahmed, UN's Yemen envoy, and the arrival in Sanaa of Stephen O'Brien, the UN humanitarian operations chief.
The UN says the conflict has killed more than 6,600 people and displaced at least three million since an Arab coalition assembled by Saudi Arabia launched operations in March 2015 in defence.
'Militia boats' targeted
Since then, the fighters have been pushed out of much of Yemen's south, but they still control nearly all of the country's Red Sea coast as well as expanses of territory around the capital Sanaa.
Earlier, Arab coalition forces launched operations against Houthi sea units after they attacked a ship reportedly carrying humanitarian supplies off Yemen's coast.
The coalition fighting the Houthis in Yemen said "air and naval forces were targeting militia boats
involved the attack".
Civilian passengers were rescued and no crew members were hurt, a statement late on Saturday said.
The vessel, an Australian-built high-speed logistics catamaran under lease to the UAE military, was attacked by Houthi fighters near the Bab el-Mandeb Strait off Yemen's southern coast on Saturday.
The coalition said the incident showed that Houthi tactics involved what it called "terrorist attacks" against civilian international navigation in the waterway.
The Houthis claimed their forces destroyed a UAE military vessel that was advancing towards the Red Sea port of Mokha.
"Armed forces destroyed with a missile a military vessel belonging to the forces of the UAE," a Houthi military official was quoted as saying by the Saba Yemeni news agency, run by the group since it seized Sanaa last year.
The vessel, belonging to the UAE Marine Dredging Company, was "on its usual route to and from Aden to transfer relief and medical aid and evacuate wounded civilians to complete their treatment outside Yemen", the coalition statement said.
Hundreds of Emirati soldiers have been fighting the Houthis and training Yemeni troops in Aden to help rebuild a state loyal to Hadi.
In 2013, more than 3.4 million barrels of oil a day passed through the 20km wide Bab el-Mandeb Strait, according to the US Energy Information Administration.
A senior Emirati commander was among dozens killed in a Tochka rocket strike in 2015 on an army camp near Bab el-Mandeb, one of the bloodiest setbacks for Gulf forces in months of fighting.
| Humanitarian agencies warn of imminent health system collapse in Yemen