(Al Jazeera English: 0730 PST, March 18, 2011) Yemeni security forces have opened fire at a protest in the capital Sanaa, killing at least 30 people. It is the highest death toll in a single day after weeks of demonstrations calling for Ali Abdullah Saleh, the Yemeni president, to stand down.

Witnesses say armed men opened fire from nearby buildings as protesters gathered in Sanaa's University Square after Friday prayers. Al Jazeera's Alan Fisher reports.

WARNING: This video contains some graphic images.