Forces loyal to Yemen's detained president have seized strategic buildings in the southern city of Aden after accusing security forces there of working for Houthi fighters who control the capital, Sanaa.
The Popular Committees of Aden said on Monday that they had wrested control of the city's main power station and intelligence headquarters from forces allied to the Houthis.
Run by former president Abd-Rabbu Mansour Hadi's brother, Nasser, the Popular Committees of Aden confirmed in a statement that several government buildings had been taken.
They also confirmed that three people were killed in the clashes.
Popular committees operate across much of Yemen, often working alongside the military in defending state buildings from attack and manning checkpoints.
Abdel Aziz bin Habtur, Aden's governor, said the situation was "under control" and denied claims that Aden's television station had been taken by the loyalists.
Hadi, a southerner, resigned in January after a prolonged power struggle with the Houthis who have controlled Sanaa since September.
On Monday, Jamal Benomar, the UN envoy to Yemen, visited Hadi who has been held under house arrest at his residence in the capital since January 22.
The Houthis, whose traditional power base is in the country's north, dissolved parliament on February 6 and installed Mohammed Ali al-Houthi, a cousin of the group's leader Abdel-Malik al-Houthi, as the new president.
On Sunday, the UN Security Council unanimously adopted a resolution demanding the group immediately relinquish control of Yemen's government.
But the resolution was not held under Chapter 7 of the UN Charter, which allows for it to be militarily enforced.
Sunday's announcement came as Yemen's neighbours, the Gulf Co-operation Council (GCC), comprising Saudi Arabia, Kuwait, Qatar, Bahrain, Oman and the United Arab Emirates threatened to intervene in the crisis.
GCC ministers had warned that if the Security Council failed to adopt a resolution allowing the use of military force "over the Houthis' illegitimate seizure of power," then they would take "measures which enable them to maintain their vital interests in the security and stability of Yemen".
To defuse the crisis, the UN has been trying to broker a power-sharing deal between the Houthis and rival political forces but with little headway.
The rise of the Houthis began last year when they descended from their heartland in northern Saada province, fighting their way towards Sanaa and defeating tribal and military rivals along the way.
The group has repeatedly rejected accusations that it wants to restore a Zaydi imamate, a theocracy that lasted for nine centuries until 1962.
Source: Al Jazeera and agencies