Southern Movement calls for protests in favour of independence amid multiple crises confronting weak central government.
Clashes between Sunni tribesmen and advancing Houthi rebels have killed hundreds of people in central Yemen, as Shia fighters continue to expand their control over more of the country.
Fighting in the past three days has reportedly killed more than 250 people as Sunni tribes backed by al-Qaeda in the Arabian Peninsula (AQAP) try to block a Houthi advance south of the capital.
The Shia rebels reportedly met stiff resistance on Monday in Bayda province, with more than 30 Houthis killed in overnight clashes.
Sources told Al Jazeera that the Qifa tribe, forced the Houthis out of the province’s Manasih area in Radaa, a town about 130km southeast of Sanaa.
The Houthis entered the AQAP stronghold of Radaa a week ago, after a commander of the army’s 193 Battalion gave up his troops’ positions.
AQAP has drawn many fighters from the town’s population of 60,000, who oppose the presence of the Houthi rebels in the mainly Sunni-populated region.
Meanwhile, the Yemeni president has criticised the Houthis’ fight against AQAP as a “bid to conquer more provinces,” describing their acts as “unacceptable”.
In a speech on Sunday, President Abd-Rabbu Mansour Hadi urged the Houthis to “immediately pull out their armed men from all the cities and provinces [they seized] including Sanaa”.
“The armed expansion of the Houthis … cannot be understood or accepted after signing the peace and national partnership agreement,” he said.
A peace agreement signed between the Houthis and the government last month, has so far has failed to end the fighting.
The Houthis, who have been accused by authorities of having links with Iran, gained control of Sanaa in September and have waged battles with opposing tribes and AQAP fighters.
Hailing from the northern highlands and championing the interests of the Zaidi community, the Houthis make up a fifth of Yemen’s 25 million population.