Yemeni officials say at least 18 people were killed and 30 wounded in clashes between troops loyal to Yemeni President Ali Abdullah Saleh and forces opposed to his rule.
Reports said Saleh's the two sides fought overnight in the capital, Sanaa, with rockets, mortars, and heavy machine guns.
Pro-regime forces have frequently fought with rival tribesmen and renegade soldiers, but the overnight fighting was reported to have been the most intense in weeks.
Saleh, Yemen's ruler for 33 years, has been clinging to power during eight months of protests calling for his ouster.
compiled from agency reports