Yemen's internationally-recognised government's Foreign Minister Mohamed al Hadrami urged Saudi Arabia to intervene against the STC's move as a guarantor of the Riyadh Agreement.
Yemen’s Southern Transitional Council (STC) has declared self-governance and a state of emergency in Aden and southern provinces.
The STC said the state of emergency would take effect at midnight on Saturday.
“The announcement by the so-called transitional council of its intention to establish a southern administration is a resumption of its armed insurgency... and an announcement of its rejection and complete withdrawal from the Riyadh agreement," Yemen's foreign ministry said in a statement on Twitter.
"The so-called transitional council will bear alone the dangerous and catastrophic consequences for such an announcement," it said.
Foreign Minister Mohamed al Hadrami urged Saudi Arabia, as a guarantor of the Riyadh Agreement, to intervene against what he described as the STC's "rebellion" in the southern provinces.
The Yemeni government blames UAE-backed separatist movements of rebelling against the government in the southern provinces and Socotra province, which comprises six islands.
Last Saturday, government forces took back control of a military camp in Socotra that was seized by STC separatists.
On April 8, the Socotra Governorate blamed the STC of conspiring to kill Governor Ramzi Mahrous.
Armed groups of the STC made a failed attempt to seize Socotra in October 2019, and UAE-backed militias raided the main airport in December and took hostages.
The UAE is part of a Saudi-led coalition that launched a massive air campaign in 2015 against Iran-aligned Houthi rebels, who overran much of Yemen, including the capital Sanaa, a year earlier.
Tens of thousands of Yemenis are since believed to have been killed and injured in the conflict, while 14 million are at risk of starvation, according to the UN.