AP:

SANAA, Yemen — Yemeni security forces firing from rooftops and houses shot at tens of thousands of anti-government demonstrators, killing at least 31 as the protesters entered a downtown square in the capital to demand the ouster of their autocratic president.

Friday's violence is the harshest response yet from President Ali Abdullah Saleh, a key — if uneasy — ally in the U.S. campaign against al-Qaida who has ruled Yemen for 30 years.

Other reports have the death toll at 33.