Yemeni security forces opened fired on demonstrators gathering for a planned march in Sanaa on Sunday, killing four people and injuring 37 others, according to a medic on the scene.
The reported violence comes a day after at least 10 people were killed and 38 others wounded in clashes in the capital, said Mohammed Al-Qubati, who works at a field hospital in Change Square, the center of the protests.
Molhim Saeed, another medic in Change Square, called Saturday "a sad day for the revolution."
"The marches were peaceful and the youth were unarmed. They refused to even fight back when they were being shot at," Saeed said.
There was no immediate comment from the government. Demonstrators have taken to the streets regularly to call for an end to the rule of President Ali Abdullah Saleh.