Thousands of Yemeni opposition activists have marched in Sana'a to demand the ouster of President Ali Abdullah Saleh, a day after fighting between pro- and anti-Saleh forces in the capital killed at least 12 people.

Yemeni medics say shooting erupted in Sana'a again Sunday as the protesters marched from Change Square, where they have been camping for much of the past 10 months to seek an end to Mr. Saleh's 33-year rule.

The medics say the gunfire killed one person and wounded at least six others. It is not clear who was responsible.

Yemeni medical officials say Saturday's clashes were between Saleh loyalists and opposition soldiers and tribesmen in Sana'a's northern Hasaba district. The 12 dead included fighters on both sides and five civilians.

Fighting between the rival forces has intensified in the Yemeni capital in recent weeks. The U.N. Security Council adopted a resolution Friday, condemning Mr. Saleh's violent crackdown on the opposition movement and urging him to sign a Gulf Cooperation Council plan for him to step down.

The GCC proposal offers Mr. Saleh immunity from prosecution if he hands power to a deputy within 30 days. Mr. Saleh has refused to sign the plan, saying he first wants international guarantees about a timetable for its implementation.