Clashes between Yemeni youths divided over a power transfer deal that grants President Ali Abdullah Saleh immunity from prosecution left 35 people injured on Tuesday, witnesses and medics said.
"Some 2,000 members of the Islamist Sunni Al-Islah (reform) party, among them dissident soldiers, attacked our camp at dawn, injuring 35 people," Khalid al-Madani, head of the camp backed by supporters of Shiite Zaidi rebels, told AFP.
Medical officials confirmed the casualty figures.
Stones and batons were wielded during the clashes in Change Square, epicentre of anti-regime protests since February and where a sit-in continues after Saleh last month signed the deal by which he will quit in February 2012.
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The attackers used sticks to destroy a podium set up by Shiite rebels at the square and stoned the camp of hundreds of activists who reject the Gulf-brokered power transfer deal, witnesses said.
They also dismantled tents, one of which serves as a field hospital, the same sources added.
Al-Islah party, which made up the largest opposition grouping during Saleh's rule, signed the deal that provides immunity to the strongman, accused of corruption and whose forces and loyalists have killed hundreds nationwide.
The Gulf deal has been rejected by both the Shiite rebels and young protesters.
Rebel commander Abdulmalik al-Huthi, slammed the attack by "Al-Islah militia" against "revolutionaries opposed to the agreement," accusing them of seeking "not to bring the criminals to justice," in a statement received by AFP.
The Huthis are Zaidi Shiites who complain of marginalisation by the Sanaa government. Thousands have been killed since a rebellion began in 2004. A ceasefire was reached in February last year.