The spokesman for the Arab coalition bombing Houthi targets in Yemen has said the kingdom and its allies will do whatever it takes to stop Yemen's second largest city from falling to the Shia rebels.
Brigadier General Ahmed Asiri, the spokesman of Operation Decisive Storm, said in Riyadh on Friday that the coalition's "main objective [is] to protect the government in Aden".
The coastal city is the last base of President Abd-Rabbu Mansour Hadi after his elected government was forced out of the capital, Sanaa.
Analysis from our correspondent
Al Jazeera's Mohamed Vall
The proclaimed aim of the Saudi-led airstrikes is to restore legitimacy in Yemen by reversing the Houthi coup. But the regional dimension is crucial.
The Houthis are a Shia group backed by Iran, a serious sectarian rival to the Sunni kingdom of Saudi Arabia. Both are regional heavyweights vying for dominance in the Middle East.
Saudi Arabia already has problems with its disgruntled Shia minority in the east of the country and a rebellious Shia community in neighbouring Bahrain.
Through Shia communities in the Arab world Iran has already gained influence in Iraq, Syria and Lebanon.
The possibility it may control Yemen with which the kingdom has 2,000km of border is very unsettling to the Saudis.
Asiri said the coalition was in complete control of Yemen's airspace and was trying to weaken the Houthis air defence system and cut off supply lines.
Civilians fleeing
Asiri's remarks came as warnings were raised that a humanitarian disaster could unfold should the conflict escalate.
Bashrahil Hesham Bashrahil, a journalist based in Aden, said civilians were scared and leaving the city with the once busy streets now eerily quiet.
"The markets are closed, businesses are closed and their is a real shortage of food," Bashrahil told Al Jazeeera.
"Banks have been shut since Thursday and will not reopen until the security situation has been addressed.
"While power supplies have not yet been effected there is a real sense of fear should the fighting worsen," he said. "Hospitals are struggling to cope with the number of injured and are appealing for blood donations."
Houthis and Hadi loyalists have been clashing on the outskirts of the city in the last few days, leaving many casualties.
Aden is believed to harbour dozens of army defectors and Houthi fighters.
Hadi left Aden on Thursday under Saudi protection. After a stop in Riyadh, he arrived on Friday in the Egyptian city of Sharm el-Sheikh where he is to attend an Arab Summit focusing on the military intervention in Yemen.
Saudi Arabia has been bombing Houthi targets since Thursday, after assembling a coalition of more than 10 countries, five of them members of the six-nation Gulf Cooperation Council.
On Friday, air strikes struck at least six provinces, with bombardment shaking Sanaa and anti-aircraft weaponry being fired in response. Civilians were fleeing from areas near military bases and installations.
Further strikes hit Saada, the main Houthi stronghold, targeting locations where the groups leader, Abdel-Malek al-Houthi might be, Yemeni military officials said.
The Houthi-run health ministry says 39 civilians have been killed in air strikes so far. Amnesty International said six children were among those killed in Sanaa on Thursday.
Egyptian and Saudi warships have been deployed to the strategic Bab al-Mandab strait, a key trade and oil route separating the Arabian Peninsula from east Africa.
An Egyptian military official told the Associated Press news agency that two destroyers and two other vessels were at the strait.
