Sanaa, Yemen (CNN) -- For the first time since the start of unrest in Yemen's capital, youth protesters numbering in the tens of thousands marched toward the Republican Palace on Monday, eyewitnesses said, in an act of defiance against President Ali Abdullah Saleh's regime. Witnesses told CNN that security forces made no move to repel the youths, who were marching in support of protests Monday in the city of Taiz, where at least 14 people were killed when security forces reportedly opened fire on demonstrators. Field medics in Taiz said more than 500 people were injured, including 154 who suffered gunshot wounds. Medical team leader Sadiq Shugaa said the field hospital "cannot give health care to all the injured, and is coordinating with hospitals outside Taiz to help the injured."
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NEW: At least 55,000 youths were marching toward the Republican Palace in Sanaa
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At least 14 reportedly were killed and hundreds injured in violent protests in Taiz
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An opposition leader urges international help to stop bloodshed
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Field hospitals are full after bloody clashes in Taiz, a medical team leader says
The youth protesters in Sanaa, whom witnesses estimated at more than 55,000, were chanting, "@placeholder wait wait, the revolution youth are coming your way!"