Anti-government forces advanced Tuesday toward President Abedrabbo Mansour Hadi's refuge of Aden in southern Yemen, fighting fierce battles with loyalist forces in which dozens of people were killed.
The Shiite Huthi militia, backed by troops allied to former president Ali Abdullah Saleh, clashed with forces loyal to Hadi in at least two southern provinces as they pushed on Aden, sources said.
In another southern city, Taez, the militia shot dead five demonstrators as protests intensified against the Huthi presence, in what Amnesty International denounced as a "shocking disregard for human life".
The militiamen have seized large parts of Yemen and, in recent days, have been moving toward Aden, where Hadi fled after escaping house arrest in the capital Sanaa last month.
Yemen, a longtime US ally in the war on Al-Qaeda, is increasingly divided between a north controlled by the Huthis, allegedly backed by Iran, and a south dominated by Hadi supporters.
The UN Security Council, Western countries and Gulf Arab monarchies have backed Hadi as the country's legitimate ruler, and his foreign minister called Monday for a Gulf intervention to confront the Huthis.
Tuesday's clashes came after the Huthis seized the airport and a nearby military base Sunday in Taez, 180 kilometres (110 miles) north of Aden and seen as a strategic entry point to Hadi's southern refuge.
Tribal sources said at least 30 people died late Monday as the Huthis and their allies clashed with tribesmen loyal to Hadi in the central Baida province and in Marib, east of Sanaa.
- Ex-president troops back Huthis -
The Huthis have been increasingly joined in the fight by troops loyal to Saleh, who resigned in 2012 following nationwide protests but has been accused of allying with the Shiite militia as he seeks to regain influence.
Military sources in south Yemen said reinforcements from the army's Al-Hamza Brigade -- still loyal to Saleh -- had been sent to the town of Qatabah, some 120 kilometres (75 miles) north of Aden.
Dozens of tanks belonging to the 133rd Brigade, also loyal to Saleh, were sent to Qatabah, military sources and witnesses said.
These troops clashed with Hadi supporters in the surrounding province and took control of the headquarters of the local government in provincial capital Daleh, military and security sources said.
Ten people were killed and several wounded in fighting for control of an army camp in northern Daleh, a military source said.
Clashes also erupted in the province of Lahj, just north of Aden, where forces loyal to Hadi had deployed in anticipation of an attack.
On Monday, Defence Minister General Mahmud al-Subeihi told troops in Kirsh, on the border between Lahj and Taez provinces, to reinforce their positions against attack.
But that was in vain, as Kirsh fell Tuesday, as did two further loyalists positions 15 kilometres down the road toward Aden, tribal sources said.
Two more civilians died in Kirsh, according to a security source.
Meanwhile, loyalists from a base at Al-Anad, in Lahj, were grouping in Aqqane, not far from Kirsh, in a bid to halt any further advance.
With authorities under increasing pressure, acting foreign minister Riyadh Yassin said Hadi had asked for military help from the six-nation Gulf Cooperation Council.
"Hadi has asked the UN and the (GCC's) Desert Shield force to intervene and confront the Huthis," Yassin said Monday on television.
"Yemen has asked the UN Security Council to impose a no-fly zone on airports seized by the Huthis," he added.
- Firing on demonstrators -
Saudi Foreign Minister Prince Saud al-Faisal had warned Monday that Arab countries may take action "to protect interests from Huthi aggression".
The Huthis, who hail from Yemen's mountainous north, have not been welcomed by the mainly Sunni residents in other parts of the country and have cracked down on protests.
Five people were killed and about 80 wounded when the Huthis opened fire Tuesday as demonstrators gathered for the third consecutive day to protest the militia's arrival in Taez, a local official and medics said.
They also shot dead three others among a crowd that protested at a Huthi base in nearby Al-Torba, a local official said.
Amnesty's Said Boumedouha said "human rights in Yemen arein free-fall as even peaceful protest becomes a life-threatening activity."
The turmoil has raised fears that extremists will exploit the security vacuum in a country already home to what Washington considers Al-Qaeda's deadliest offshoot.
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