Yemeni Shiite rebels seized a strategic port city Tuesday to widen their fast-expanding zone of control, hours after a new premier was named in a bid to defuse the country's political crisis.
And with the weakening of central authority, battered by the rebels' seizure of Sanaa last month, southern separatists were stepping up their demands for independence.
The Huthi Shiite rebels met little resistance as they overran Hudeida, taking control of Yemen's second most important seaport, a security official said.
The operation came just hours after President Abdrabuh Mansur Hadi named a new prime minister in an effort to appease the rebels.
"Huthi militants are deployed across vital installations, including the airport and the port" in Hudeida, the official said.
Military and rebel sources confirmed that Huthi militants were seen deployed across main roads in the city of more than two million residents.
Witnesses and local sources said the militants had set up checkpoints at the city's main entrances, with a security guard reported killed when the rebels seized a court building.
The takeover came just weeks after the Huthis, almost unopposed, swept into the capital Sanaa, 225 kilometres (140 miles) to the east.
The rebels, traditionally based in the north, have been battling troops and Sunni militants in recent months as part of their bid to spread their control across the country.
Huthi militiamen stormed into Sanaa on September 21, seizing key government installations, and they now man checkpoints and run patrols across the capital in almost total absence of the security forces.
The impoverished and predominantly Sunni country has been wracked by political turmoil and sporadic violence since an uprising toppled strongman Ali Abdullah Saleh in 2012.
Yemen is also facing security threats from Al-Qaeda in the Arabian Peninsula (AQAP) and a southern separatist movement.
On Tuesday, suspected Al-Qaeda militants shot dead an army officer in the southern province of Shabwa, a military source said.
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Rival militants appear to be exploiting a power vacuum in Yemen, which is located next to oil-rich Saudi Arabia and key shipping routes in the Gulf of Aden.
Military sources had previously warned that Shiite rebels had their sights set on Hudeida and on extending their presence to the narrow Bab al-Mandab strait, which leads to the Suez canal.
- 'Benefit from changes' -
And in the east of the country, the Huthis are apparently eyeing Yemen's oil and gas reserves in Marib province.
Hadi on Monday named Yemen's envoy to the UN, Khalid Bahah, as the new premier, after the rebels rejected an earlier choice.
Bahah's nomination, which appeared to have the support of the rebels, was expected to be a key step in persuading them to withdraw from Sanaa.
With the political crisis mounting in Sanaa, tens of thousands of supporters of the separatist Southern Movement gathered in Aden on Tuesday to press demands for the south's independence, an AFP correspondent reported.
The demonstration in the largest city of the south, called by hardliners in the Southern Movement, came on the 51st anniversary of the south's revolt against British colonial rule.
The exiled president of the former South Yemen, Ali Salem al-Baid, who champions secession, urged supporters to seize the opportunity to demand independence.
"All ongoing developments fall in the interest of the southern people's justified call for freedom ... We must swiftly benefit from these changes," he said in a statement received by AFP.
Protesters pitched tents in central Aden's Al-Arood Square at the launch of what they said would be an indefinite sit-in.
"We swear by God: Sanaa will not rule over us," chanted the protesters, who raised flags of the former South Yemen.
The south was independent between the end of British colonial rule in 1967 and its union with the north in 1990.
A secession attempt four years later sparked a brief but bloody civil war that ended with northern forces occupying the region.
The separatists, as well as Huthi Shiites, rejected plans unveiled in February for Yemen to become a six-region federation, including two for the south, as part of a post-Saleh political transition.