Meanwhile, Yemen President Abedrabbo Mansour Hadi ordered his forces to cease-fire immediately in interim capital Aden after fierce clashes with southern separatists.
"They are moving militarily, setting up new military checkpoints and attacking camps of the legitimacy (government).", Ahmed bin Dahr wrote in a message on his Facebook page, referring to southern fighters under the separatist Southern Transitional Council (STC).
Fighting subsided late on Sunday evening as both sides ordered their forces to stand down.
"This is a serious matter and the coalition and Arabs as a whole must move to save the situation".
The Southern Transitional Council (STC) - a movement demanding secession for southern Yemen - had given Hadi's government a seven-day ultimatum last week to either dismiss his prime minister and cabinet, or face an overthrow.
The separatists have been backing the government against the Houthis, but long-simmering tensions have flared in recent weeks, with the separatists accusing the government of corruption and discrimination.
Armed separatists appeared to gain the upper hand by wresting a key military base and several government buildings from soldiers loyal to Hadi, local newspaper Aden al-Ghad reported on its website.
Gunmen were deployed throughout most of Aden's districts and there was heavy automatic gunfire and explosions in the southern port city, according to Reuters witnesses.
UAE entered Yemen's war in March 2015 as part of a Saudi-led coalition seeking to remove Houthi rebels.
Bin Daghr had earlier denounced the separatists' actions as a coup and said the outcome of the contest in Aden was in the hands of their backers, the UAE, who enjoy overall control in the city, and warned that the situation was headed toward "a comprehensive military confrontation".
The forces from Abyan progressed towards Aden after clashes with government forces on the way, they said. UAE is fighting against the internationally recognised Govt of Hadi who is living in exile in Saudi Arabia.
The Huthis have increasingly consolidated their grip on Sanaa and the north, especially since rebels killed Saleh in December after their alliance collapsed.
They seized the capital in 2014, prompting the Saudi-led coalition to intervene on the side of the government.
Three quarters of Yemen's population - 22.2 million people - need assistance, including 8.4 million people who are considered severely food insecure and at risk of starvation.
The years of conflict and a blockade imposed by the coalition have caused what the United Nations calls "the worst man-made humanitarian crisis of our time".