At least 20 people were killed in the southern Yemeni city of Taiz when security forces stormed the anti-government sit-in, Al Arabiya broadcaster reported Monday, DPA reported.
At least 150 people were injured in the clashes between protesters and security forces. Some 37 of those injured were taken by security from hospitals, the channel added.
Government forces also set the protest camps on fire.
Widespread demonstrations demanding President Ali Abdullah Saleh step down from power have shaken Yemen for months, and are often met with brutal crackdowns by security forces.