Saudi Arabia's navy evacuated dozens of diplomats from Yemen on Saturday and the United Nations pulled out international staff after a third night of Saudi-led air strikes trying to stem advances by Iranian-allied Houthi fighters.
Residents reported heavy clashes between the Houthis and mainly Sunni tribal fighters in the south of the country, while the air campaign sought to stall a fresh offensive by the Shi'ite Muslim group on Aden from the east.
Riyadh's intervention, a surprise move from a conservative monarchy better known for flexing its muscle in oil markets than through military might, is planned to last a month but could extend for five or six, a Gulf diplomatic source said.
He said satellite imagery had shown in January that the Houthis had repositioned long-range Scud missiles in the north, close to the Saudi border and aimed at Saudi territory. A Yemeni official said Iran, which says it has not armed the Houthis, was providing parts for the missiles.
Eighty-six foreign diplomats and Saudi nationals were shipped out of Aden to the Red Sea port of Jeddah, a Saudi military officer said, escaping the city where President Abd-Rabbu Mansour Hadi had taken refuge until Thursday, when he left for Egypt to shore up Arab support for his crumbling authority.
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The director general of Yemen's Health Ministry, al-Khadher Laswar, said more than 68 people had been killed and 452 wounded in the city since Wednesday. Explosions at Aden's largest ammunition depot on Saturday killed at least 15 people and wounded dozens, he said.
In the capital Sanaa, which has been under Houthi control since September, the United Nations said most of its 100 international staff were evacuated. Airport officials said up to 250 other foreigners working for international oil companies and NGOs also flew out to Ethiopia and Djibouti.
Houthi fighters seeking to overthrow the Western- and Saudi-backed Hadi have continued to make gains since the Saudi-led coalition launched air strikes against them on Thursday.