In Riyadh, Yemen’s Prime Minister Khaled Bahah was sworn in as vice president at the country’s embassy in front of exiled President Abedrabbo Mansour Hadi, a day after his appointment, in a move welcomed by Yemen’s Gulf neighbours.
Yemen’s main southern city of Aden saw the heaviest fighting overnight, with medics and military forces saying at least 30 people were killed in clashes between rebels and supporters of Mr Hadi.
Residents said warplanes from a Saudi-led coalition of countries pounded the rebel-held presidential complex and other positions in Aden, Mr Hadi’s last refuge before he fled to neighbouring Saudi Arabia as the air war began on March 26.
The Houthi rebels, who have joined with forces loyal to ex-president Ali Abdullah Saleh, advanced on Aden last month after seizing control of the capital Sanaa last year.
Saudi Arabia has accused Iran of backing the rebel offensive and rallied support from regional allies for the coalition.
Western powers have also backed Mr Hadi as Yemen’s ruler, while the United Nations has called for a resumption of UN-brokered talks aimed at bringing stability to the country.
Heavy fighting in Aden on Sunday night left at least 13 civilians, 11 rebels and six pro-Hadi fighters dead, medical and military sources said.
Humanitarian groups have struggled to bring aid into the country and said the situation in Aden was deteriorating rapidly.
“Shops are closed. We have a problem of food,” said Marie-Elisabeth Ingres, the Yemen representative of Doctors Without Borders (MSF).
Metaz Al Maisuri, an activist living in Aden, said basic services had stopped and there had been a “mass exodus” of civilians from the city.
“Schools, universities and all public and private facilities have been shut due” to the violence, he told AFP.
“Residents’ lives have become very difficult and complicated… They can no longer obtain the food they need,” he said.
“We are unable to leave our houses to buy what we need because of the Houthi snipers,” said Adwaa Mubarak, a 48-year-old woman in Aden.
“Our living conditions are bad. Bakeries are shut,” she said, alleging that several people had been shot dead as they queued to buy bread.
Aid workers said Sanaa was also suffering as air strikes hit rebel positions and supplies dwindled.
“There is a food and water shortage. People are unable to move,” said Marie Claire Feghali, the Red Cross spokeswoman in Yemen.
Thousands of foreigners have been trapped by the fighting, with the International Organisation for Migration saying more than 16,000 are stranded in Yemen.
Coalition air strikes also hit Houthi positions in the southern Shabwa province, witnesses said.
Armed tribesmen in the province seized a rebel army brigade base in the coastal town of Al Nashima, tribal sources said.
Tribesmen also seized control of army bases assigned with protecting Balhaf port, location of the country’s only gas export terminal, tribal and military sources said.
Soldiers from two army brigades based near the port abandoned their positions, and tribesmen who had besieged the bases advanced and seized heavy weaponry, the sources said.
The bases are a few kilometres from the gas plant, in which France’s Total has an almost 40 per cent interest.
Foreign workers had already been evacuated to Djibouti because of intensified fighting and exports had stopped, an employee at the plant said.
The two brigades were assigned with protecting the port and related installations, including gas pipelines stretching from Marib province, east of Sanaa, a military official said.
A special force of around 400 soldiers was still based within the terminal zone which had not been approached by the armed tribes, the official added.