Fighting between Houthi rebels and loyalists of former president Ali Abdullah Saleh broke out in the Yemeni capital Sanaa early Saturday.
The violence erupted after Houthi rebels attempted to arrest Brigadier Tarek Saleh, a nephew of the former president, according to an Anadolu Agency reporter.
Explosions and gunfire could be heard across Sanaa.
No reports are yet available about casualties.
Saleh loyalists are reported to have captured several areas in eastern Sanaa and military checkpoints along the road between Sanaa and Dhamar province.
Forces loyal to the former president reportedly overran a military camp in southern Sanaa, according to Saleh's General People's Congress.
A source in Saleh's forces said hundreds of tribesmen were ordered to move to Sanaa to back up loyalists of the former president against Houthi rebels.
The fresh violence came after the two allies failed to broker a truce to halt three days of infighting in the Yemeni capital.
There was no comment from the Houthi rebel group on the fresh violence.
Houthis and Saleh loyalists jointly overran Sanaa and much of the country in 2014, forcing the internationally recognized government of President Abd Rabbuh Mansour Hadi to flee to Saudi Arabia.
In 2015, Saudi Arabia and its Arab allies launched a massive air campaign to reverse Houthi military gains and shore up the Yemeni government.
The conflict has since claimed more than 10,000 lives and triggered what the United Nations has described as the world's worst humanitarian crisis.
