Yemen crisis: Houthi rebels push into southern areas
Fighters from Yemen's Houthi rebel movement are advancing into southern Yemen, clashing with forces allied to President Abdrabbuh Mansour Hadi.
Rebels and soldiers loyal to Mr Hadi's ousted predecessor reportedly entered the provincial capital of Dhalea and the Red Sea port of Mukha on Tuesday.
Pro-Houthi troops also killed at least four people protesting in and around the third city of Taizz, medics said.
Mr Hadi has called on the Gulf Co-operation Council (GCC) to intervene.
His foreign minister said on Monday that a request was made after warplanes targeted the palace in the southern port city of Aden that has been the president's base since he fled Sanaa last month.
The rebels placed Mr Hadi under effective house arrest when they took full control of the capital in January and declared that a five-member "presidential council" would rule the country.
On Tuesday, Houthi fighters and soldiers loyal to former President Ali Abdullah Saleh armed with artillery, anti-aircraft guns and machine-guns were battling militiamen and tribesmen loyal to Mr Hadi in Dhalea, security officials and residents said.
The Associated Press cited witnesses as saying the rebels had seized the governor's office.
Dhalea, about 78km (48 miles) east of Taizz, is the capital of a province with the same name and a hotbed of separatists seeking an independent South Yemen.
The rebels also entered Mukha, 88km (54 miles) west of Taizz, the Reuters news agency reported.
The port is a short drive from the strategically important Bab al-Mandab strait, which connects the Red Sea to the Gulf of Aden and is a vital shipping lane for oil tankers.
In Taizz, which the rebels captured at the weekend, and the nearby village of Turba there were clashes between anti-Houthi protesters and police commandos loyal to Mr Saleh.
Witnesses said the commandos fired live bullets, tear gas and baton rounds at the protesters to disperse them. Medics said at least four people were killed and several others wounded.
Late on Monday, at least 15 rebel fighters and nine pro-Hadi tribesmen were killed in clashes in the central province of al-Bayda, tribal sources told the AFP news agency. Another six tribesmen died in fighting in Marib province, east of Sanaa, the sources said.
The rebel advance comes a day after Yemen's foreign minister revealed in an interview with the Saudi-owned newspaper Asharq al-Awsat that President Hadi had called on the GCC to send its Peninsula Shield force to intervene militarily and prevent the fall of Aden.
Riad Yassin urged the GCC and the United Nations to impose a no-fly zone and ban the use of warplanes from airports and airbases controlled by the Houthis and Mr Saleh.
The Houthis: A minority Shia from the north, the group seized control of Sanaa last year and have since been expanding their control.
President Hadi: Backed by military and police loyalists, and by militia known as Popular Resistance Committees, he is trying to fight back against the rebels from his stronghold in the south.
Al-Qaeda in the Arabian Peninsula: Seen by the US as the most dangerous branch of al-Qaeda, AQAP opposes both the Houthis and forces loyal to President Hadi.
Islamic State: A Yemeni affiliate of IS has recently emerged, which seeks to eclipse AQAP.
Saudi Arabia's Foreign Minister Saud al-Faisal meanwhile warned: "If the Houthi coup does not end peacefully, we will take the necessary measures for this crisis to protect the region."
The UN special adviser on Yemen, Jamal Benomar, told the BBC that the Saudis had "good reasons" to be concerned.
But he added: "I don't think any side could win a civil war. No side can win a civil war - the only way forward is negotiation, which implies concession from all sides, which implies also, a compromise."
On Saturday, President Hadi accused the Zaidi Shia-led rebels of mounting "a coup against constitutional legitimacy" and of being a proxy for regional Shia power Iran.
The Houthis' Supreme Revolutionary Committee did not respond directly to the speech, but announced a "general mobilisation" of the armed forces to combat the "dirty war" it said was being waged by Hadi loyalists.